1
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Meneghini G, Brem S, Malic E. Excitonic Thermalization Bottleneck in Twisted TMD Heterostructures. NANO LETTERS 2024; 24:4505-4511. [PMID: 38578047 DOI: 10.1021/acs.nanolett.4c00450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/06/2024]
Abstract
Twisted van der Waals heterostructures show intriguing interface exciton physics, including hybridization effects and emergence of moiré potentials. Recent experiments have revealed that moiré-trapped excitons exhibit remarkable dynamics, where excited states show lifetimes that are several orders of magnitude longer than in monolayers. The origin of this behavior is still under debate. Based on a microscopic many-particle approach, we investigate the phonon-driven relaxation cascade of nonequilibrium moiré excitons in the exemplary MoSe2-WSe2 heterostructure. We track exciton relaxation pathways across different moiré mini-bands and identify the phonon-scattering channels assisting the spatial redistribution of excitons into low-energy pockets of the moiré potential. We unravel a phonon bottleneck in the flat band structure at low twist angles preventing excitons from fully thermalizing into the lowest state, explaining the measured enhanced emission intensity and lifetime of excited moiré excitons. Overall, our work provides important insights into exciton relaxation dynamics in flat-band exciton materials.
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Affiliation(s)
- Giuseppe Meneghini
- Department of Physics, Philipps University of Marburg, 35037 Marburg, Germany
| | - Samuel Brem
- Department of Physics, Philipps University of Marburg, 35037 Marburg, Germany
| | - Ermin Malic
- Department of Physics, Philipps University of Marburg, 35037 Marburg, Germany
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2
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Knorr W, Brem S, Meneghini G, Malic E. Polaron-induced changes in moiré exciton propagation in twisted van der Waals heterostructures. NANOSCALE 2024. [PMID: 38623653 DOI: 10.1039/d4nr00136b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/17/2024]
Abstract
Twisted transition metal dichalcogenides (TMDs) present an intriguing platform for exploring excitons and their transport properties. By introducing a twist angle, a moiré superlattice forms, providing a spatially dependent exciton energy landscape. Based on a microscopic many-particle theory, we investigate in this work polaron-induced changes in exciton transport properties in the exemplary MoSe2/WSe2 heterostructure. We demonstrate that polaron formation and the associated enhancement of the moiré exciton mass lead to a significant band flattening. As a result, the moiré inter-cell tunneling and the propagation velocity undergo noticeable temperature and twist-angle dependent changes. We predict a reduction of the hopping strength ranging from 80% at a twist angle of 1° to 30% at 3° at room temperature. The provided microscopic insights into the spatio-temporal exciton dynamics in presence of a moiré potential further expand the possibilities to tune charge and energy transport in 2D materials.
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Affiliation(s)
- Willy Knorr
- Department of Physics, Philipps University, 35037 Marburg, Germany.
| | - Samuel Brem
- Department of Physics, Philipps University, 35037 Marburg, Germany.
| | | | - Ermin Malic
- Department of Physics, Philipps University, 35037 Marburg, Germany.
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3
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Bange JP, Schmitt D, Bennecke W, Meneghini G, AlMutairi A, Watanabe K, Taniguchi T, Steil D, Steil S, Weitz RT, Jansen GSM, Hofmann S, Brem S, Malic E, Reutzel M, Mathias S. Probing electron-hole Coulomb correlations in the exciton landscape of a twisted semiconductor heterostructure. SCIENCE ADVANCES 2024; 10:eadi1323. [PMID: 38324690 PMCID: PMC10849592 DOI: 10.1126/sciadv.adi1323] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Accepted: 01/10/2024] [Indexed: 02/09/2024]
Abstract
In two-dimensional semiconductors, cooperative and correlated interactions determine the material's excitonic properties and can even lead to the creation of correlated states of matter. Here, we study the fundamental two-particle correlated exciton state formed by the Coulomb interaction between single-particle holes and electrons. We find that the ultrafast transfer of an exciton's hole across a type II band-aligned semiconductor heterostructure leads to an unexpected sub-200-femtosecond upshift of the single-particle energy of the electron being photoemitted from the two-particle exciton state. While energy relaxation usually leads to an energetic downshift of the spectroscopic signature, we show that this upshift is a clear fingerprint of the correlated interaction of the electron and hole parts of the exciton. In this way, time-resolved photoelectron spectroscopy is straightforwardly established as a powerful method to access electron-hole correlations and cooperative behavior in quantum materials. Our work highlights this capability and motivates the future study of optically inaccessible correlated excitonic and electronic states of matter.
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Affiliation(s)
- Jan Philipp Bange
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - David Schmitt
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Wiebke Bennecke
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Giuseppe Meneghini
- Fachbereich Physik, Philipps-Universität Marburg, 35032 Marburg, Germany
| | | | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Daniel Steil
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Sabine Steil
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - R. Thomas Weitz
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
- International Center for Advanced Studies of Energy Conversion (ICASEC), University of Göttingen, Göttingen, Germany
| | - G. S. Matthijs Jansen
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Stephan Hofmann
- Department of Engineering, University of Cambridge, Cambridge CB3 0FA, UK
| | - Samuel Brem
- Fachbereich Physik, Philipps-Universität Marburg, 35032 Marburg, Germany
| | - Ermin Malic
- Fachbereich Physik, Philipps-Universität Marburg, 35032 Marburg, Germany
- Department of Physics, Chalmers University of Technology, Gothenburg, Sweden
| | - Marcel Reutzel
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Stefan Mathias
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
- International Center for Advanced Studies of Energy Conversion (ICASEC), University of Göttingen, Göttingen, Germany
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4
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Liu H, Wang J, Chen S, Sun Z, Xu H, Han Y, Wang C, Liu H, Huang L, Luo J, Liu D. Direct Visualization of Dark Interlayer Exciton Transport in Moiré Superlattices. NANO LETTERS 2024; 24:339-346. [PMID: 38147355 DOI: 10.1021/acs.nanolett.3c04105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2023]
Abstract
Moiré superlattices have emerged as an unprecedented manipulation tool for engineering correlated quantum phenomena in van der Waals heterostructures. With moiré potentials as a naturally configurable solid-state that sustains high exciton density, interlayer excitons in transition metal dichalcogenide heterostructures are expected to achieve high-temperature exciton condensation. However, the exciton degeneracy state is usually optically inactive due to the finite momentum of interlayer excitons. Experimental observation of dark interlayer excitons in moiré potentials remains challenging. Here we directly visualize the dark interlayer exciton transport in WS2/h-BN/WSe2 heterostructures using femtosecond transient absorption microscopy. We observe a transition from classical free exciton gas to quantum degeneracy by imaging temperature-dependent exciton transport. Below a critical degeneracy temperature, exciton diffusion rates exhibit an accelerating downward trend, which can be explained well by a nonlinear quantum diffusion model. These results open the door to quantum information processing and high-precision metrology in moiré superlattices.
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Affiliation(s)
- Huan Liu
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
| | - Jiangcai Wang
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
| | - Shihong Chen
- School of Resources, Environment and Materials, Guangxi University, Nanning 530004, China
| | - Zejun Sun
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
| | - Haowen Xu
- Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing 100083, China
| | - Yishu Han
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
| | - Chong Wang
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
| | - Huixian Liu
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
| | - Li Huang
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
| | - Jianbin Luo
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
| | - Dameng Liu
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
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5
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Günder D, Axt M, Witte G. Heteroepitaxy in Organic/TMD Hybrids and Challenge to Achieve it for TMD Monolayers: The Case of Pentacene on WS 2 and WSe 2. ACS APPLIED MATERIALS & INTERFACES 2024; 16:1911-1920. [PMID: 38154080 DOI: 10.1021/acsami.3c15829] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2023]
Abstract
The intriguing photophysical properties of monolayer stacks of different transition-metal dichalcogenides (TMDs), revealing rich exciton physics including interfacial and moiré excitons, have recently prompted an extension of similar investigations to hybrid systems of TMDs and organic films, as the latter combine large photoabsorption cross sections with the ability to tailor energy levels by targeted synthesis. To go beyond single-molecule photoexcitations and exploit the excitonic signatures of organic solids, crystalline molecular films are required. Moreover, a defined registry on the substrate, ideally an epitaxy, is desirable to also achieve an excitonic coupling in momentum space. This poses a certain challenge as excitonic dipole moments of organic films are closely related to the molecular orientation and film structure, which critically depend on the support roughness. Using X-ray diffraction, optical polarization, and atomic force microscopy, we analyzed the structure of pentacene (PEN) multilayer films grown on WSe2(001) and WS2(001) and identified an epitaxial alignment. While (022)-oriented PEN films are formed on both substrates, their azimuthal orientations are quite different, showing an alignment of the molecular L-axis along the ⟨ 110 ⟩ WSe 2 and ⟨ 100 ⟩ WS 2 directions. This intrinsic epitaxial PEN growth depends, however, sensitively on the substrates surface quality. While it occurs on exfoliated TMD single crystals and multilayer flakes, it is hardly found on exfoliated monolayers, which often exhibit bubbles and wrinkles. This enhances the surface roughness and results in (001)-oriented PEN films with upright molecular orientation but without any azimuthal alignment. However, monolayer flakes can be smoothed by AFM operated in contact mode or by transferring to ultrasmooth substrates such as hBN, which again yields epitaxial PEN films. As different PEN orientations result in different characteristic film morphologies (elongated mesa islands vs pyramidal dendrites), which can be easily distinguished by AFM or optical microscopy, this provides a simple means to judge the roughness of the used TMD surface.
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Affiliation(s)
- Darius Günder
- Molekulare Festkörperphysik, Philipps-Universität Marburg, Marburg 35032, Germany
| | - Marleen Axt
- Oberflächenphysik, Philipps-Universität Marburg, Marburg 35032, Germany
| | - Gregor Witte
- Molekulare Festkörperphysik, Philipps-Universität Marburg, Marburg 35032, Germany
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6
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Wietek E, Florian M, Göser J, Taniguchi T, Watanabe K, Högele A, Glazov MM, Steinhoff A, Chernikov A. Nonlinear and Negative Effective Diffusivity of Interlayer Excitons in Moiré-Free Heterobilayers. PHYSICAL REVIEW LETTERS 2024; 132:016202. [PMID: 38242648 DOI: 10.1103/physrevlett.132.016202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Accepted: 11/10/2023] [Indexed: 01/21/2024]
Abstract
Interlayer exciton diffusion is studied in atomically reconstructed MoSe_{2}/WSe_{2} heterobilayers with suppressed disorder. Local atomic registry is confirmed by characteristic optical absorption, circularly polarized photoluminescence, and g-factor measurements. Using transient microscopy we observe propagation properties of interlayer excitons that are independent from trapping at moiré- or disorder-induced local potentials. Confirmed by characteristic temperature dependence for free particles, linear diffusion coefficients of interlayer excitons at liquid helium temperature and low excitation densities are almost 1000 times higher than in previous observations. We further show that exciton-exciton repulsion and annihilation contribute nearly equally to nonlinear propagation by disentangling the two processes in the experiment and simulations. Finally, we demonstrate effective shrinking of the light emission area over time across several hundreds of picoseconds at the transition from exciton- to the plasma-dominated regimes. Supported by microscopic calculations for band gap renormalization to identify the Mott threshold, this indicates transient crossing between rapidly expanding, short-lived electron-hole plasma and slower, long-lived exciton populations.
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Affiliation(s)
- Edith Wietek
- Institute of Applied Physics and Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062 Dresden, Germany
| | - Matthias Florian
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Jonas Göser
- Fakultät für Physik, Munich Quantum Center, and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität München, 80539 München, Germany
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Alexander Högele
- Fakultät für Physik, Munich Quantum Center, and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität München, 80539 München, Germany
- Munich Center for Quantum Science and Technology (MCQST), 80799 München, Germany
| | | | - Alexander Steinhoff
- Institut für Theoretische Physik, Universität Bremen, 28334 Bremen, Germany
- Bremen Center for Computational Materials Science, Universität Bremen, 28334 Bremen, Germany
| | - Alexey Chernikov
- Institute of Applied Physics and Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062 Dresden, Germany
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7
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You B, Xu Z, Yang J, Jiang X, Li Y, Shao G, Jin Y, Xiang H, Jiang H, Liu X, Sun J, Feng Y, Jiang Y, Pan A, Liu S. Interlayer Coupling in Anisotropic/Isotropic Van der Waals Heterostructures of ReS 2 and WS 2. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024; 20:e2304010. [PMID: 37726234 DOI: 10.1002/smll.202304010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Revised: 09/05/2023] [Indexed: 09/21/2023]
Abstract
Van der Waals (vdW) heterostructures are composed of atomically thin layers assembled through weak (vdW) force, which have opened a new era for integrating materials with distinct properties and specific applications. However, few studies have focused on whether and how anisotropic materials affect heterostructure system. The study introduces anisotropic and isotropic materials in a heterojunction system to change the in-plane symmetry, offering a new degree of freedom for modulating its properties. The sample is fabricated by manually stacking ReS2 and WS2 flakes prepared by mechanical exfoliation. Raman spectra and photoluminescence measurements confirm the formation of an effective heterojunction, indicating interlayer coupling of the system. The anisotropy and asymmetry of the WS2 -ReS2 heterostructure system can be adjusted by the introduction of isotropic WS2 and anisotropic ReS2 , which can be proved by the change of the polarized Raman pattern. In the transient absorption measurement, the transient absorption spectra of WS2 -ReS2 heterostructure are red-shifted compared to those of WS2 monolayer, and the charge transfer is observed in the heterostructure. These results show the potential of anisotropic 2D materials in anisotropy modulation of heterostructures, which may promote future electronic or photonic application.
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Affiliation(s)
- Bingying You
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, P. R. China
- Photonics Research Group, Ghent University-imec, Ghent, 9000, Belgium
| | - Zheyuan Xu
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan Institute of Optoelectronic Integration, College of Materials Science and Engineering, Hunan University, Changsha, 410082, P. R. China
| | - Junqiang Yang
- School of Physics and Electronics, Central South University, Changsha, 410083, P. R. China
| | - Xingxing Jiang
- School of Physics and Electronics, Hunan University, Changsha, 410082, P. R. China
| | - Yanfang Li
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, P. R. China
| | - Gonglei Shao
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, P. R. China
| | - Yuanyuan Jin
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, P. R. China
| | - Haiyan Xiang
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, P. R. China
| | - Huili Jiang
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, P. R. China
| | - Xiaochi Liu
- School of Physics and Electronics, Central South University, Changsha, 410083, P. R. China
| | - Jian Sun
- School of Physics and Electronics, Central South University, Changsha, 410083, P. R. China
| | - Yexing Feng
- School of Physics and Electronics, Hunan University, Changsha, 410082, P. R. China
| | - Ying Jiang
- School of Physics and Electronics, Hunan University, Changsha, 410082, P. R. China
| | - Anlian Pan
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan Institute of Optoelectronic Integration, College of Materials Science and Engineering, Hunan University, Changsha, 410082, P. R. China
| | - Song Liu
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, P. R. China
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8
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Guo S, Li C, Nie Z, Wang X, Wang M, Tian C, Yan X, Hu K, Long R. Tensile Strain-Dependent Ultrafast Electron Transfer and Relaxation Dynamics in Flexible WSe 2/MoS 2 Heterostructures. J Phys Chem Lett 2023:10920-10929. [PMID: 38033191 DOI: 10.1021/acs.jpclett.3c02943] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2023]
Abstract
Understanding and controlling carrier dynamics in two-dimensional (2D) van der Waals heterostructures through strain are crucial for their flexible applications. Here, femtosecond transient absorption spectroscopy is employed to elucidate the interlayer electron transfer and relaxation dynamics under external tensile strains in a WSe2/MoS2 heterostructure. The results show that a modest ∼1% tensile strain can significantly alter the lifetimes of electron transfer and nonradiative electron-hole recombination by >30%. Ab initio non-adiabatic molecular dynamics simulations suggest that tensile strain weakens the electron-phonon coupling, thereby suppressing the transfer and recombination dynamics. Theoretical predictions indicate that strain-induced energy difference increases along the electron transfer path could contribute to the prolongation of the transfer lifetime. A subpicosecond decay process, related to hot-electron cooling, remains almost unaffected by strain. This study demonstrates the potential of tuning interlayer carrier dynamics through external strains, offering insights into flexible optoelectronic device design with 2D materials.
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Affiliation(s)
- Sen Guo
- School of Physical Science and Information Technology, Liaocheng University, Liaocheng, Shandong 252000, China
- FSchool of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006, China
| | - Chaofan Li
- School of Physical Science and Information Technology, Liaocheng University, Liaocheng, Shandong 252000, China
| | - Zhaogang Nie
- School of Physical Science and Information Technology, Liaocheng University, Liaocheng, Shandong 252000, China
- FSchool of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006, China
| | - Xiaoli Wang
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of the Ministry of Education, Beijing Normal University, Beijing 100875, China
| | - Minghong Wang
- School of Physical Science and Information Technology, Liaocheng University, Liaocheng, Shandong 252000, China
| | - Cunwei Tian
- School of Physical Science and Information Technology, Liaocheng University, Liaocheng, Shandong 252000, China
| | - Xinhua Yan
- Nobat Intelligent Equipment (Shandong), Company, Ltd., Liaocheng, Shandong 252000, China
| | - Kaige Hu
- FSchool of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006, China
| | - Run Long
- College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of the Ministry of Education, Beijing Normal University, Beijing 100875, China
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9
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Policht VR, Mittenzwey H, Dogadov O, Katzer M, Villa A, Li Q, Kaiser B, Ross AM, Scotognella F, Zhu X, Knorr A, Selig M, Cerullo G, Dal Conte S. Time-domain observation of interlayer exciton formation and thermalization in a MoSe 2/WSe 2 heterostructure. Nat Commun 2023; 14:7273. [PMID: 37949848 PMCID: PMC10638375 DOI: 10.1038/s41467-023-42915-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Accepted: 10/26/2023] [Indexed: 11/12/2023] Open
Abstract
Vertical heterostructures of transition metal dichalcogenides (TMDs) host interlayer excitons with electrons and holes residing in different layers. With respect to their intralayer counterparts, interlayer excitons feature longer lifetimes and diffusion lengths, paving the way for room temperature excitonic optoelectronic devices. The interlayer exciton formation process and its underlying physical mechanisms are largely unexplored. Here we use ultrafast transient absorption spectroscopy with a broadband white-light probe to simultaneously resolve interlayer charge transfer and interlayer exciton formation dynamics in a MoSe2/WSe2 heterostructure. We observe an interlayer exciton formation timescale nearly an order of magnitude (~1 ps) longer than the interlayer charge transfer time (~100 fs). Microscopic calculations attribute this relative delay to an interplay of a phonon-assisted interlayer exciton cascade and thermalization, and excitonic wave-function overlap. Our results may explain the efficient photocurrent generation observed in optoelectronic devices based on TMD heterostructures, as the interlayer excitons are able to dissociate during thermalization.
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Affiliation(s)
- Veronica R Policht
- Department of Physics, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano, 20133, Italy.
- NRC Postdoc residing at U.S. Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC, 20375, USA.
| | - Henry Mittenzwey
- Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universität Berlin, Hardenbergstraße 36, 10623, Berlin, Germany.
| | - Oleg Dogadov
- Department of Physics, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano, 20133, Italy
| | - Manuel Katzer
- Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universität Berlin, Hardenbergstraße 36, 10623, Berlin, Germany
| | - Andrea Villa
- Department of Physics, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano, 20133, Italy
| | - Qiuyang Li
- Department of Chemistry, Columbia University, 3000 Broadway, New York, NY, 10027, USA
| | | | - Aaron M Ross
- Department of Physics, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano, 20133, Italy
| | - Francesco Scotognella
- Department of Physics, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano, 20133, Italy
- Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, Torino, 10129, Italy
| | - Xiaoyang Zhu
- Department of Chemistry, Columbia University, 3000 Broadway, New York, NY, 10027, USA
| | - Andreas Knorr
- Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universität Berlin, Hardenbergstraße 36, 10623, Berlin, Germany
| | - Malte Selig
- Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universität Berlin, Hardenbergstraße 36, 10623, Berlin, Germany
| | - Giulio Cerullo
- Department of Physics, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano, 20133, Italy
- CNR-IFN, Piazza Leonardo da Vinci 32, Milano, 20133, Italy
| | - Stefano Dal Conte
- Department of Physics, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano, 20133, Italy.
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10
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Sun X, Lu Z, Lu Y. Enhanced interactions of excitonic complexes in free-standing WS 2. NANOSCALE 2023. [PMID: 37937449 DOI: 10.1039/d3nr04594c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2023]
Abstract
Excitonic complexes, bound states of electrons and holes, provide a promising platform in monolayer transition-metal dichalcogenide (TMDC) semiconductors for investigating diverse many-body interaction phenomena. The surrounding dielectric environment has been found to strongly influence the excitonic properties of the TMDC monolayers. While the impact of different dielectric surroundings on two-dimensional semiconductor materials and their strong correlations have been well studied, the effects on exciton formation and its properties resulting from a further reduction in dielectric screening remain elusive. In this study, we examined free-standing tungsten disulfide (WS2) monolayers, where the efficient generation of higher-order correlated excitonic complexes is readily observed. This phenomenon arises from the effective mutual interactions among excitons and internal carriers, attributed to the modulated exciton dynamics generated by the further reduced dielectric screening effect in the freestanding structure. The formation efficiency of excitonic complexes is enhanced and the multiple biexciton species (five particles such as charged biexcitons and acceptor/donor-bound biexcitons) are successfully induced under low excitation intensity and moderate temperature conditions. Our findings offer valuable insights into the influence of the dielectric environment on exciton interactions and enable a productive avenue for exploring fundamental many-body interactions, providing new possibilities for dielectric engineering of atomic thin semiconductors.
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Affiliation(s)
- Xueqian Sun
- School of Engineering, College of Engineering and Computer Science, the Australian National University, Canberra, ACT, 2601, Australia
| | - Zhuoyuan Lu
- School of Engineering, College of Engineering and Computer Science, the Australian National University, Canberra, ACT, 2601, Australia
| | - Yuerui Lu
- School of Engineering, College of Engineering and Computer Science, the Australian National University, Canberra, ACT, 2601, Australia
- Australian Research Council Centre of Excellence for Quantum Computation and Communication Technology, the Australian National University, Canberra, ACT, 2601, Australia.
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11
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Fang H, Lin Q, Zhang Y, Thompson J, Xiao S, Sun Z, Malic E, Dash SP, Wieczorek W. Localization and interaction of interlayer excitons in MoSe 2/WSe 2 heterobilayers. Nat Commun 2023; 14:6910. [PMID: 37903787 PMCID: PMC10616232 DOI: 10.1038/s41467-023-42710-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Accepted: 10/19/2023] [Indexed: 11/01/2023] Open
Abstract
Transition metal dichalcogenide (TMD) heterobilayers provide a versatile platform to explore unique excitonic physics via the properties of the constituent TMDs and external stimuli. Interlayer excitons (IXs) can form in TMD heterobilayers as delocalized or localized states. However, the localization of IX in different types of potential traps, the emergence of biexcitons in the high-excitation regime, and the impact of potential traps on biexciton formation have remained elusive. In our work, we observe two types of potential traps in a MoSe2/WSe2 heterobilayer, which result in significantly different emission behavior of IXs at different temperatures. We identify the origin of these traps as localized defect states and the moiré potential of the TMD heterobilayer. Furthermore, with strong excitation intensity, a superlinear emission behavior indicates the emergence of interlayer biexcitons, whose formation peaks at a specific temperature. Our work elucidates the different excitation and temperature regimes required for the formation of both localized and delocalized IX and biexcitons and, thus, contributes to a better understanding and application of the rich exciton physics in TMD heterostructures.
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Affiliation(s)
- Hanlin Fang
- Department of Microtechnology and Nanoscience (MC2), Chalmers University of Technology, 41296, Gothenburg, Sweden.
| | - Qiaoling Lin
- Department of Electrical and Photonics Engineering, Technical University of Denmark, DK-2800, Kongens Lyngby, Denmark
| | - Yi Zhang
- Department of Electronics and Nanoengineering and QTF Centre of Excellence, Aalto University, Espoo, 02150, Finland
| | - Joshua Thompson
- Department of Physics, Philipps-Universität Marburg, 35037, Marburg, Germany
| | - Sanshui Xiao
- Department of Electrical and Photonics Engineering, Technical University of Denmark, DK-2800, Kongens Lyngby, Denmark
| | - Zhipei Sun
- Department of Electronics and Nanoengineering and QTF Centre of Excellence, Aalto University, Espoo, 02150, Finland
| | - Ermin Malic
- Department of Physics, Philipps-Universität Marburg, 35037, Marburg, Germany
| | - Saroj P Dash
- Department of Microtechnology and Nanoscience (MC2), Chalmers University of Technology, 41296, Gothenburg, Sweden
| | - Witlef Wieczorek
- Department of Microtechnology and Nanoscience (MC2), Chalmers University of Technology, 41296, Gothenburg, Sweden.
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12
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Yagodkin D, Kumar A, Ankerhold E, Richter J, Watanabe K, Taniguchi T, Gahl C, Bolotin KI. Probing the Formation of Dark Interlayer Excitons via Ultrafast Photocurrent. NANO LETTERS 2023; 23:9212-9218. [PMID: 37788809 PMCID: PMC10603811 DOI: 10.1021/acs.nanolett.3c01708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Revised: 08/15/2023] [Indexed: 10/05/2023]
Abstract
Optically dark excitons determine a wide range of properties of photoexcited semiconductors yet are hard to access via conventional time-resolved spectroscopies. Here, we develop a time-resolved ultrafast photocurrent technique (trPC) to probe the formation dynamics of optically dark excitons. The nonlinear nature of the trPC makes it particularly sensitive to the formation of excitons occurring at the femtosecond time scale after the excitation. As a proof of principle, we extract the interlayer exciton formation time of 0.4 ps at 160 μJ/cm2 fluence in a MoS2/MoSe2 heterostructure and show that this time decreases with fluence. In addition, our approach provides access to the dynamics of carriers and their interlayer transport. Overall, our work establishes trPC as a technique to study dark excitons in various systems that are hard to probe by other approaches.
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Affiliation(s)
- Denis Yagodkin
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
| | - Abhijeet Kumar
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
| | - Elias Ankerhold
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
| | - Johanna Richter
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
| | - Kenji Watanabe
- Research
Center for Functional Materials, National
Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- International
Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Cornelius Gahl
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
| | - Kirill I. Bolotin
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
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13
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Zheng SW, Wang HY, Wang H, Wang L. Excitonic Effect Drives Ultrafast Transition in Two-Dimensional Transition Metal Dichalcogenides. J Phys Chem Lett 2023; 14:9200-9206. [PMID: 37801730 DOI: 10.1021/acs.jpclett.3c02545] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/08/2023]
Abstract
Two-dimensional (2D) transition metal dichalcogenides (TMDCs) are ideal platforms for exploring excitonic physics because of the tightly bound excitons. In this work, we observed the onset of band-edge exciton formation in monolayer MoS2 (WS2) and bilayer MoS2-WS2 by measuring the transient optical response upon excitation with ultrashort laser pulses. In addition to wavelength dependence on excitation under nonresonant excitation, we found that the onset of band-edge exciton formation in monolayer MoS2 (WS2) pumped in the exciton state is significantly faster than that with pumping in the nonexciton state, which could be attributed to the effective transition between exciton states induced by the excitonic effect. Besides, the onset of band-edge exciton formation in van der Waals heterostructures is similar to that for monolayer TMDCs regardless of charge transfer at the interface. Our work contributes to a better understanding of exciton dynamics in 2D TMDCs, providing a solid basis of the rational design of the 2D optoelectronic applications based on TMDCs.
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Affiliation(s)
- Shu-Wen Zheng
- Henan Key Laboratory of Infrared Materials & Spectrum Measures and Applications School of Physics, Henan Normal University, 46 Jianshe Road, Xinxiang 453007, China
| | - Hai-Yu Wang
- State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, 2699 Qianjin Street, Changchun 130012, China
| | - Hai Wang
- State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, 2699 Qianjin Street, Changchun 130012, China
| | - Lei Wang
- State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, 2699 Qianjin Street, Changchun 130012, China
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14
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Qin Y, Wang R, Wu X, Wang Y, Li X, Gao Y, Peng L, Gong Q, Liu Y. Ultrafast Electronic Dynamics in Anisotropic Indirect Interlayer Excitonic States of Monolayer WSe 2/ReS 2 Heterojunctions. NANO LETTERS 2023; 23:8643-8649. [PMID: 37672749 DOI: 10.1021/acs.nanolett.3c02488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/08/2023]
Abstract
Understanding ultrafast electronic dynamics of the interlayer excitonic states in atomically thin transition metal dichalcogenides is of importance in engineering valleytronics and developing excitonic integrated circuits. In this work, we experimentally explored the ultrafast dynamics of indirect interlayer excitonic states in monolayer type II WSe2/ReS2 heterojunctions using time-resolved photoemission electron microscopy, which reveals its anisotropic behavior. The ultrafast cooling and decay of excited-state electrons exhibit significant linear dichroism. The ab initio theoretical calculations provide unambiguous evidence that this linear dichroism result is primarily associated with the anisotropic nonradiative recombination of indirect interlayer excitonic states. Measuring time-resolved photoemission energy spectra, we have further revealed the ultrafast evolution of excited-state electrons in anisotropic indirect interlayer excitonic states. The findings have important implications for controlling the interlayer moiré excitonic effects and designing anisotropic optoelectronic devices.
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Affiliation(s)
- Yulu Qin
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-Optoelectronics, School of Physics, Peking University, Beijing 100871, China
| | - Rui Wang
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-Optoelectronics, School of Physics, Peking University, Beijing 100871, China
| | - Xiaoyuan Wu
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-Optoelectronics, School of Physics, Peking University, Beijing 100871, China
| | - Yunkun Wang
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-Optoelectronics, School of Physics, Peking University, Beijing 100871, China
| | - Xiaofang Li
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-Optoelectronics, School of Physics, Peking University, Beijing 100871, China
| | - Yunan Gao
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-Optoelectronics, School of Physics, Peking University, Beijing 100871, China
| | - Liangyou Peng
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-Optoelectronics, School of Physics, Peking University, Beijing 100871, China
| | - Qihuang Gong
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-Optoelectronics, School of Physics, Peking University, Beijing 100871, China
- Peking University Yangtze Delta Institute of Optoelectronics, Nantong, Jiangsu 226010, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, China
| | - Yunquan Liu
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-Optoelectronics, School of Physics, Peking University, Beijing 100871, China
- Peking University Yangtze Delta Institute of Optoelectronics, Nantong, Jiangsu 226010, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, China
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15
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Troue M, Figueiredo J, Sigl L, Paspalides C, Katzer M, Taniguchi T, Watanabe K, Selig M, Knorr A, Wurstbauer U, Holleitner AW. Extended Spatial Coherence of Interlayer Excitons in MoSe_{2}/WSe_{2} Heterobilayers. PHYSICAL REVIEW LETTERS 2023; 131:036902. [PMID: 37540866 DOI: 10.1103/physrevlett.131.036902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Accepted: 06/09/2023] [Indexed: 08/06/2023]
Abstract
We report on the spatial coherence of interlayer exciton ensembles as formed in MoSe_{2}/WSe_{2} heterostructures and characterized by point-inversion Michelson-Morley interferometry. Below 10 K, the measured spatial coherence length of the interlayer excitons reaches values equivalent to the lateral expansion of the exciton ensembles. In this regime, the light emission of the excitons turns out to be homogeneously broadened in energy with a high temporal coherence. At higher temperatures, both the spatial coherence length and the temporal coherence time decrease, most likely because of thermal processes. The presented findings point towards a spatially extended, coherent many-body state of interlayer excitons at low temperature.
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Affiliation(s)
- Mirco Troue
- Walter Schottky Institute and Physics Department, Technical University of Munich, Am Coulombwall 4a, 85748 Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), Schellingstr. 4, 80799 Munich, Germany
| | - Johannes Figueiredo
- Walter Schottky Institute and Physics Department, Technical University of Munich, Am Coulombwall 4a, 85748 Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), Schellingstr. 4, 80799 Munich, Germany
| | - Lukas Sigl
- Walter Schottky Institute and Physics Department, Technical University of Munich, Am Coulombwall 4a, 85748 Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), Schellingstr. 4, 80799 Munich, Germany
| | - Christos Paspalides
- Walter Schottky Institute and Physics Department, Technical University of Munich, Am Coulombwall 4a, 85748 Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), Schellingstr. 4, 80799 Munich, Germany
| | - Manuel Katzer
- Institute for Theoretical Physics, Nonlinear Optics and Quantum Electronics, Technical University of Berlin, 10623 Berlin, Germany
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Malte Selig
- Institute for Theoretical Physics, Nonlinear Optics and Quantum Electronics, Technical University of Berlin, 10623 Berlin, Germany
| | - Andreas Knorr
- Institute for Theoretical Physics, Nonlinear Optics and Quantum Electronics, Technical University of Berlin, 10623 Berlin, Germany
| | - Ursula Wurstbauer
- Institute of Physics, Münster University, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
| | - Alexander W Holleitner
- Walter Schottky Institute and Physics Department, Technical University of Munich, Am Coulombwall 4a, 85748 Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), Schellingstr. 4, 80799 Munich, Germany
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16
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Erkensten D, Brem S, Perea-Causín R, Hagel J, Tagarelli F, Lopriore E, Kis A, Malic E. Electrically tunable dipolar interactions between layer-hybridized excitons. NANOSCALE 2023; 15:11064-11071. [PMID: 37309577 PMCID: PMC10324325 DOI: 10.1039/d3nr01049j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Accepted: 06/02/2023] [Indexed: 06/14/2023]
Abstract
Transition-metal dichalcogenide bilayers exhibit a rich exciton landscape including layer-hybridized excitons, i.e. excitons which are of partly intra- and interlayer nature. In this work, we study hybrid exciton-exciton interactions in naturally stacked WSe2 homobilayers. In these materials, the exciton landscape is electrically tunable such that the low-energy states can be rendered more or less interlayer-like depending on the strength of the external electric field. Based on a microscopic and material-specific many-particle theory, we reveal two intriguing interaction regimes: a low-dipole regime at small electric fields and a high-dipole regime at larger fields, involving interactions between hybrid excitons with a substantially different intra- and interlayer composition in the two regimes. While the low-dipole regime is characterized by weak inter-excitonic interactions between intralayer-like excitons, the high-dipole regime involves mostly interlayer-like excitons which display a strong dipole-dipole repulsion and give rise to large spectral blue-shifts and a highly anomalous diffusion. Overall, our microscopic study sheds light on the remarkable electrical tunability of hybrid exciton-exciton interactions in atomically thin semiconductors and can guide future experimental studies in this growing field of research.
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Affiliation(s)
- Daniel Erkensten
- Department of Physics, Chalmers University of Technology, 41296 Gothenburg, Sweden.
| | - Samuel Brem
- Department of Physics, Philipps-Universität Marburg, 35037 Marburg, Germany
| | - Raül Perea-Causín
- Department of Physics, Chalmers University of Technology, 41296 Gothenburg, Sweden.
| | - Joakim Hagel
- Department of Physics, Chalmers University of Technology, 41296 Gothenburg, Sweden.
| | - Fedele Tagarelli
- Institute of Electrical and Microengineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
- Institute of Materials Science and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Edoardo Lopriore
- Institute of Electrical and Microengineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
- Institute of Materials Science and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Andras Kis
- Institute of Electrical and Microengineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
- Institute of Materials Science and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Ermin Malic
- Department of Physics, Philipps-Universität Marburg, 35037 Marburg, Germany
- Department of Physics, Chalmers University of Technology, 41296 Gothenburg, Sweden.
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17
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Brem S, Malic E. Bosonic Delocalization of Dipolar Moiré Excitons. NANO LETTERS 2023; 23:4627-4633. [PMID: 37184441 DOI: 10.1021/acs.nanolett.3c01160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
In superlattices of twisted semiconductor monolayers, tunable moiré potentials emerge, trapping excitons into periodic arrays. In particular, spatially separated interlayer excitons are subject to a deep potential landscape and they exhibit a permanent dipole providing a unique opportunity to study interacting bosonic lattices. Recent experiments have demonstrated density-dependent transport properties of moiré excitons, which could play a key role for technological applications. However, the intriguing interplay between exciton-exciton interactions and moiré trapping has not been well understood yet. In this work, we develop a microscopic theory of interacting excitons in external potentials allowing us to tackle this highly challenging problem. We find that interactions between moiré excitons lead to a delocalization at intermediate densities, and we show how this transition can be tuned via twist angle and temperature. The delocalization is accompanied by a modification of optical moiré resonances, which gradually merge into a single free exciton peak.
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Affiliation(s)
- Samuel Brem
- Department of Physics, Philipps University, 35037 Marburg, Germany
| | - Ermin Malic
- Department of Physics, Philipps University, 35037 Marburg, Germany
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18
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Tagarelli F, Lopriore E, Erkensten D, Perea-Causín R, Brem S, Hagel J, Sun Z, Pasquale G, Watanabe K, Taniguchi T, Malic E, Kis A. Electrical control of hybrid exciton transport in a van der Waals heterostructure. NATURE PHOTONICS 2023; 17:615-621. [PMID: 37426431 PMCID: PMC10322698 DOI: 10.1038/s41566-023-01198-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Accepted: 03/10/2023] [Indexed: 07/11/2023]
Abstract
Interactions between out-of-plane dipoles in bosonic gases enable the long-range propagation of excitons. The lack of direct control over collective dipolar properties has so far limited the degrees of tunability and the microscopic understanding of exciton transport. In this work we modulate the layer hybridization and interplay between many-body interactions of excitons in a van der Waals heterostructure with an applied vertical electric field. By performing spatiotemporally resolved measurements supported by microscopic theory, we uncover the dipole-dependent properties and transport of excitons with different degrees of hybridization. Moreover, we find constant emission quantum yields of the transporting species as a function of excitation power with radiative decay mechanisms dominating over nonradiative ones, a fundamental requirement for efficient excitonic devices. Our findings provide a complete picture of the many-body effects in the transport of dilute exciton gases, and have crucial implications for studying emerging states of matter such as Bose-Einstein condensation and optoelectronic applications based on exciton propagation.
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Affiliation(s)
- Fedele Tagarelli
- Institute of Electrical and Microengineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
- Institute of Materials Science and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Edoardo Lopriore
- Institute of Electrical and Microengineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
- Institute of Materials Science and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Daniel Erkensten
- Department of Physics, Chalmers University of Technology, Gothenburg, Sweden
| | - Raül Perea-Causín
- Department of Physics, Chalmers University of Technology, Gothenburg, Sweden
| | - Samuel Brem
- Department of Physics, Philipps-Universität Marburg, Marburg, Germany
| | - Joakim Hagel
- Department of Physics, Chalmers University of Technology, Gothenburg, Sweden
| | - Zhe Sun
- Institute of Electrical and Microengineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
- Institute of Materials Science and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Gabriele Pasquale
- Institute of Electrical and Microengineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
- Institute of Materials Science and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
| | - Ermin Malic
- Department of Physics, Chalmers University of Technology, Gothenburg, Sweden
- Department of Physics, Philipps-Universität Marburg, Marburg, Germany
| | - Andras Kis
- Institute of Electrical and Microengineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
- Institute of Materials Science and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
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19
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Spin-polarized spatially indirect excitons in a topological insulator. Nature 2023; 614:249-255. [PMID: 36755173 DOI: 10.1038/s41586-022-05567-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Accepted: 11/16/2022] [Indexed: 02/10/2023]
Abstract
The exciton, a bound state of an electron and a hole, is a fundamental quasiparticle induced by coherent light-matter interactions in semiconductors. When the electrons and holes are in distinct spatial locations, spatially indirect excitons are formed with a much longer lifetime and a higher condensation temperature. One of the ultimate frontiers in this field is to create long-lived excitonic topological quasiparticles by driving exciton states with topological properties, to simultaneously leverage both topological effects and correlation1,2. Here we reveal the existence of a transient excitonic topological surface state (TSS) in a topological insulator, Bi2Te3. By using time-, spin- and angle-resolved photoemission spectroscopy, we directly follow the formation of a long-lived exciton state as revealed by an intensity buildup below the bulk-TSS mixing point and an anomalous band renormalization of the continuously connected TSS in the momentum space. Such a state inherits the spin-polarization of the TSS and is spatially indirect along the z axis, as it couples photoinduced surface electrons and bulk holes in the same momentum range, which ultimately leads to an excitonic state of the TSS. These results establish Bi2Te3 as a possible candidate for the excitonic condensation of TSSs3 and, in general, opens up a new paradigm for exploring the momentum space emergence of other spatially indirect excitons, such as moiré and quantum well excitons4-6, and for the study of non-equilibrium many-body topological physics.
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20
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Nie X, Wu X, Wang Y, Ban S, Lei Z, Yi J, Liu Y, Liu Y. Surface acoustic wave induced phenomena in two-dimensional materials. NANOSCALE HORIZONS 2023; 8:158-175. [PMID: 36448884 DOI: 10.1039/d2nh00458e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Surface acoustic wave (SAW)-matter interaction provides a fascinating key for inducing and manipulating novel phenomena and functionalities in two-dimensional (2D) materials. The dynamic strain field and piezo-electric field associated with propagating SAWs determine the coherent manipulation and transduction between 2D excitons and phonons. Over the past decade, many intriguing acoustic-induced effects, including the acousto-electric effect, acousto-galvanic effect, acoustic Stark effect, acoustic Hall effect and acoustic exciton transport, have been reported experimentally. However, many more phenomena, such as the valley acousto-electric effect, valley acousto-electric Hall effect and acoustic spin Hall effect, were only theoretically proposed, the experimental verification of which are yet to be achieved. In this minireview, we attempt to overview the recent breakthrough of SAW-induced phenomena covering acoustic charge transport, acoustic exciton transport and modulation, and coherent acoustic phonons. Perspectives on the opportunities of the proposed SAW-induced phenomena, as well as open experimental challenges, are also discussed, attempting to offer some guidelines for experimentalists and theorists to explore the desired exotic properties and boost practical applications of 2D materials.
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Affiliation(s)
- Xuchen Nie
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control of Mechanical Structures, and Institute for Frontier Science, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, China.
| | - Xiaoyue Wu
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control of Mechanical Structures, and Institute for Frontier Science, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, China.
| | - Yang Wang
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control of Mechanical Structures, and Institute for Frontier Science, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, China.
| | - Siyuan Ban
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control of Mechanical Structures, and Institute for Frontier Science, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, China.
| | - Zhihao Lei
- Global Innovative Centre for Advanced Nanomaterials, College of Engineering, Science and Environment, The University of Newcastle, NSW, 2308, Australia
| | - Jiabao Yi
- Global Innovative Centre for Advanced Nanomaterials, College of Engineering, Science and Environment, The University of Newcastle, NSW, 2308, Australia
| | - Ying Liu
- College of Jincheng, Nanjing University of Aeronautics and Astronautics, Nanjing 211156, China.
| | - Yanpeng Liu
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control of Mechanical Structures, and Institute for Frontier Science, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, China.
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21
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Thompson JJP, Lumsargis V, Feierabend M, Zhao Q, Wang K, Dou L, Huang L, Malic E. Interlayer exciton landscape in WS 2/tetracene heterostructures. NANOSCALE 2023; 15:1730-1738. [PMID: 36594632 DOI: 10.1039/d2nr02055f] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
The vertical stacking of two-dimensional materials into heterostructures gives rise to a plethora of intriguing optoelectronic properties and presents an unprecedented potential for technological development. While much progress has been made combining different monolayers of transition metal dichalcogenides (TMDs), little is known about TMD-based heterostructures including organic layers of molecules. Here, we present a joint theory-experiment study on a TMD/tetracene heterostructure demonstrating clear signatures of spatially separated interlayer excitons in low temperature photoluminescence spectra. Here, the Coulomb-bound electrons and holes are localized either in the TMD or in the molecule layer, respectively. We reveal both in theory and experiment signatures of the entire intra- and interlayer exciton landscape in the photoluminescence spectra. In particular, we find both in theory and experiment a pronounced transfer of intensity from the intralayer TMD exciton to a series of energetically lower interlayer excitons with decreasing temperature. In addition, we find signatures of phonon-sidebands stemming from these interlayer exciton states. Our findings shed light on the microscopic nature of interlayer excitons in TMD/molecule heterostructures and could have important implications for technological applications of these materials.
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Affiliation(s)
- Joshua J P Thompson
- Department of Physics, Philipps-Universität Marburg, 35037 Marburg, Germany.
| | - Victoria Lumsargis
- Department of Chemistry, Purdue University, West Lafayette, Indiana, 47907, USA
| | - Maja Feierabend
- Department of Physics, Chalmers University of Technology, 412 96 Gothenburg, Sweden
| | - Quichen Zhao
- Department of Chemistry, Purdue University, West Lafayette, Indiana, 47907, USA
- State Key Laboratory of Superhard Materials, Jilin University, Changchun, Jilin, 130012, China
| | - Kang Wang
- Davidson School of Chemical Engineering, Purdue University, West Lafayette, Indiana, 47907, USA
| | - Letian Dou
- Davidson School of Chemical Engineering, Purdue University, West Lafayette, Indiana, 47907, USA
| | - Libai Huang
- Department of Chemistry, Purdue University, West Lafayette, Indiana, 47907, USA
| | - Ermin Malic
- Department of Physics, Philipps-Universität Marburg, 35037 Marburg, Germany.
- Department of Physics, Chalmers University of Technology, 412 96 Gothenburg, Sweden
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22
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Martins Quintela MFC, Peres NMR. Wannier excitons confined in hexagonal boron nitride triangular quantum dots. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 35:035302. [PMID: 36368044 DOI: 10.1088/1361-648x/aca24f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Accepted: 11/11/2022] [Indexed: 06/16/2023]
Abstract
With the ever-growing interest in quantum computing, understanding the behavior of excitons in monolayer quantum dots has become a topic of great relevance. In this paper, we consider a Wannier exciton confined in a triangular quantum dot of hexagonal boron nitride. We begin by outlining the adequate basis functions to describe a particle in a triangular enclosure, analyzing their degeneracy and symmetries. Afterwards, we discuss the excitonic Hamiltonian inside the quantum dot and study the influence of the quantum dot dimensions on the excitonic states.
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Affiliation(s)
- M F C Martins Quintela
- Department of Physics and Centre of Physics of the Universities of Minho and Porto (CF-UM-UP), Campus of Gualtar, 4710-057 Braga, Portugal
- International Iberian Nanotechnology Laboratory (INL), Av. Mestre José Veiga, 4715-330 Braga, Portugal
| | - N M R Peres
- Department of Physics and Centre of Physics of the Universities of Minho and Porto (CF-UM-UP), Campus of Gualtar, 4710-057 Braga, Portugal
- International Iberian Nanotechnology Laboratory (INL), Av. Mestre José Veiga, 4715-330 Braga, Portugal
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23
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Sun X, Zhu Y, Qin H, Liu B, Tang Y, Lü T, Rahman S, Yildirim T, Lu Y. Enhanced interactions of interlayer excitons in free-standing heterobilayers. Nature 2022; 610:478-484. [PMID: 36224395 DOI: 10.1038/s41586-022-05193-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2021] [Accepted: 08/04/2022] [Indexed: 11/09/2022]
Abstract
Strong, long-range dipole-dipole interactions between interlayer excitons (IXs) can lead to new multiparticle correlation regimes1,2, which drive the system into distinct quantum and classical phases2-5, including dipolar liquids, crystals and superfluids. Both repulsive and attractive dipole-dipole interactions have been theoretically predicted between IXs in a semiconductor bilayer2,6-8, but only repulsive interactions have been reported experimentally so far3,9-16. This study investigated free-standing, twisted (51°, 53°, 45°) tungsten diselenide/tungsten disulfide (WSe2/WS2) heterobilayers, in which we observed a transition in the nature of dipolar interactions among IXs, from repulsive to attractive. This was caused by quantum-exchange-correlation effects, leading to the appearance of a robust interlayer biexciton phase (formed by two IXs), which has been theoretically predicted6-8 but never observed before in experiments. The reduced dielectric screening in a free-standing heterobilayer not only resulted in a much higher formation efficiency of IXs, but also led to strongly enhanced dipole-dipole interactions, which enabled us to observe the many-body correlations of pristine IXs at the two-dimensional quantum limit. In addition, we firstly observed several emission peaks from moiré-trapped IXs at room temperature in a well-aligned, free-standing WSe2/WS2 heterobilayer. Our findings open avenues for exploring new quantum phases with potential for applications in non-linear optics.
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Affiliation(s)
- Xueqian Sun
- School of Engineering, College of Engineering and Computer Science, the Australian National University, Canberra, Australian Capital Territory, Australia
| | - Yi Zhu
- School of Engineering, College of Engineering and Computer Science, the Australian National University, Canberra, Australian Capital Territory, Australia
| | - Hao Qin
- School of Engineering, College of Engineering and Computer Science, the Australian National University, Canberra, Australian Capital Territory, Australia
| | - Boqing Liu
- School of Engineering, College of Engineering and Computer Science, the Australian National University, Canberra, Australian Capital Territory, Australia
| | - Yilin Tang
- School of Engineering, College of Engineering and Computer Science, the Australian National University, Canberra, Australian Capital Territory, Australia
| | - Tieyu Lü
- Department of Physics and Institute of Theoretical Physics and Astrophysics, Xiamen University, Xiamen, China
| | - Sharidya Rahman
- School of Engineering, College of Engineering and Computer Science, the Australian National University, Canberra, Australian Capital Territory, Australia
| | - Tanju Yildirim
- Center for Functional Sensor and Actuator, Research Center for Functional Materials, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki, Japan
| | - Yuerui Lu
- School of Engineering, College of Engineering and Computer Science, the Australian National University, Canberra, Australian Capital Territory, Australia. .,Australian Research Council Centre of Excellence for Quantum Computation and Communication Technology, the Australian National University, Canberra, Australian Capital Territory, Australia.
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24
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Yu Y, Shen T, Long H, Zhong M, Xin K, Zhou Z, Wang X, Liu YY, Wakabayashi H, Liu L, Yang J, Wei Z, Deng HX. Doping Engineering in the MoS 2 /SnSe 2 Heterostructure toward High-Rejection-Ratio Solar-Blind UV Photodetection. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2206486. [PMID: 36047665 DOI: 10.1002/adma.202206486] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2022] [Revised: 08/19/2022] [Indexed: 06/15/2023]
Abstract
The intentionally designed band alignment of heterostructures and doping engineering are keys to implement device structure design and device performance optimization. According to the theoretical prediction of several typical materials among the transition metal dichalcogenides (TMDs) and group-IV metal chalcogenides, MoS2 and SnSe2 present the largest staggered band offset. The large band offset is conducive to the separation of photogenerated carriers, thus MoS2 /SnSe2 is a theoretically ideal candidate for fabricating photodetector, which is also verified in the experiment. Furthermore, in order to extend the photoresponse spectrum to solar-blind ultraviolet (SBUV), doping engineering is adopted to form an additional electron state, which provides an extra carrier transition channel. In this work, pure MoS2 /SnSe2 and doped MoS2 /SnSe2 heterostructures are both fabricated. In terms of the photoelectric performance evaluation, the rejection ratio R254 /R532 of the photodetector based on doped MoS2 /SnSe2 is five orders of magnitude higher than that of pure MoS2 /SnSe2 , while the response time is obviously optimized by 3 orders. The results demonstrate that the combination of band alignment and doping engineering provides a new pathway for constructing SBUV photodetectors.
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Affiliation(s)
- Yali Yu
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Tao Shen
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Haoran Long
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Mianzeng Zhong
- Hunan Key Laboratory of Nanophotonics and Devices, School of Physics and Electronics, Central South University, Changsha, 410083, China
| | - Kaiyao Xin
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Ziqi Zhou
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xiaoyu Wang
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yue-Yang Liu
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083, China
| | - Hitoshi Wakabayashi
- EE Department, School of Engineering, Tokyo Institute of Technology, Yokohama, 226-8502, Japan
| | - Liyuan Liu
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Juehan Yang
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083, China
| | - Zhongming Wei
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Hui-Xiong Deng
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, 100049, China
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25
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Ye L, Xu X, He S, Liu Y, Jin Y, Yang YM, Zhu H. Molecular Triplet Sensitization of Monolayer Semiconductors in 2D Organic/Inorganic Hybrid Heterostructures. ACS NANO 2022; 16:12532-12540. [PMID: 35900068 DOI: 10.1021/acsnano.2c03995] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Hybrid heterostructures (HSs) comprising organic and two-dimensional (2D) monolayer semiconductors hold great promise for optoelectronic applications. So far, research efforts on organic/2D HSs have exclusively focused on coupling directly photoexcited singlets to monolayer semiconductors. It remains unexplored whether and how the optically dark triplets in organic semiconductors with intriguing properties (e.g., long lifetime) can be implemented for modulating light-matter interactions of hybrid HSs. Herein, we investigate the triplet sensitization of monolayer semiconductors by time-resolved spectroscopic studies on Pd-octaethylporphyrin (PdOEP)/WSe2 and PdOEP/WS2 HSs with type I and type II band alignment, respectively. We show that PdOEP triplets formed in ∼5 ps from intersystem crossing can transfer energy or charge to WSe2 or WS2 monolayers, respectively, leading to a significant photoluminescence enhancement (180%) in WSe2 or long-lived charge separation (>2 ns) in WS2. The triplet transfer occurs in ∼100 ns, which is more than 3 orders of magnitude slower than singlet and can be attributed to its tightly localized nature. Further study of thickness dependence reveals the dictating role of triplet diffusion for triplet sensitization in organic/2D HSs. This study shows the great promise of much less explored molecular triplets on sensitizing 2D monolayer semiconductors and provides the guidance to achieve long-range light harvesting and energy migration in organic/2D HSs for enhanced optoelectronic applications.
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Affiliation(s)
- Lei Ye
- Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou 310027, China
- ZJU-Hangzhou Global Scientific and Technological Innovation Center, Hangzhou 310014, China
| | - Xuehui Xu
- State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, Zhejiang University, Hangzhou 310027, China
| | - Siyu He
- Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Yanping Liu
- Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Yizheng Jin
- Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Yang Michael Yang
- State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, Zhejiang University, Hangzhou 310027, China
| | - Haiming Zhu
- Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou 310027, China
- ZJU-Hangzhou Global Scientific and Technological Innovation Center, Hangzhou 310014, China
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26
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Usman A, Adel Aly M, Masenda H, Thompson JJP, Gunasekera SM, Mucha-Kruczyński M, Brem S, Malic E, Koch M. Enhanced excitonic features in an anisotropic ReS 2/WSe 2 heterostructure. NANOSCALE 2022; 14:10851-10861. [PMID: 35838641 DOI: 10.1039/d2nr01973f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Two-dimensional (2D) semiconductors have opened new horizons for future optoelectronic applications through efficient light-matter and many-body interactions at quantum level. Anisotropic 2D materials like rhenium disulphide (ReS2) present a new class of materials with polarized excitonic resonances. Here, we demonstrate a WSe2/ReS2 heterostructure which exhibits a significant photoluminescence quenching at room temperature as well as at low temperatures. This indicates an efficient charge transfer due to the electron-hole exchange interaction. The band alignment of two materials suggests that electrons optically injected into WSe2 are transferred to ReS2. Polarization resolved luminescence measurements reveal two additional polarization-sensitive exciton peaks in ReS2 in addition to the two conventional exciton resonances X1 and X2. Furthermore, for ReS2 we observe two charged excitons (trions) with binding energies of 18 meV and 15 meV, respectively. The bi-excitons of WSe2 become polarization sensitive and inherit polarizing properties from the underlying ReS2 layers, which act as patterned substrates for top layer. Overall, our findings provide a better understanding of optical signatures in 2D anisotropic materials.
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Affiliation(s)
- Arslan Usman
- Department of Physics and Materials Sciences Centre, Philipps-Universität Marburg, Marburg 35032, Germany.
- Department of Physics, COMSATS University Islamabad-Lahore-Campus, Pakistan
| | - M Adel Aly
- Department of Physics and Materials Sciences Centre, Philipps-Universität Marburg, Marburg 35032, Germany.
- Department of Physics, Faculty of Science, Ain Shams University, Cairo 11566, Egypt
| | - Hilary Masenda
- Department of Physics and Materials Sciences Centre, Philipps-Universität Marburg, Marburg 35032, Germany.
- School of Physics, University of the Witwatersrand, 2050 Johannesburg, South Africa
| | - Joshua J P Thompson
- Department of Physics and Materials Sciences Centre, Philipps-Universität Marburg, Marburg 35032, Germany.
| | | | - Marcin Mucha-Kruczyński
- Department of Physics, University of Bath, Claverton Down, Bath BA2 7AY, UK
- Centre for Nanoscience and Nanotechnology, University of Bath, Claverton Down, Bath BA2 7AY, UK
| | - Samuel Brem
- Department of Physics and Materials Sciences Centre, Philipps-Universität Marburg, Marburg 35032, Germany.
| | - Ermin Malic
- Department of Physics and Materials Sciences Centre, Philipps-Universität Marburg, Marburg 35032, Germany.
| | - Martin Koch
- Department of Physics and Materials Sciences Centre, Philipps-Universität Marburg, Marburg 35032, Germany.
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27
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Formation of moiré interlayer excitons in space and time. Nature 2022; 608:499-503. [PMID: 35978130 DOI: 10.1038/s41586-022-04977-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Accepted: 06/14/2022] [Indexed: 11/09/2022]
Abstract
Moiré superlattices in atomically thin van der Waals heterostructures hold great promise for extended control of electronic and valleytronic lifetimes1-7, the confinement of excitons in artificial moiré lattices8-13 and the formation of exotic quantum phases14-18. Such moiré-induced emergent phenomena are particularly strong for interlayer excitons, where the hole and the electron are localized in different layers of the heterostructure19,20. To exploit the full potential of correlated moiré and exciton physics, a thorough understanding of the ultrafast interlayer exciton formation process and the real-space wavefunction confinement is indispensable. Here we show that femtosecond photoemission momentum microscopy provides quantitative access to these key properties of the moiré interlayer excitons. First, we elucidate that interlayer excitons are dominantly formed through femtosecond exciton-phonon scattering and subsequent charge transfer at the interlayer-hybridized Σ valleys. Second, we show that interlayer excitons exhibit a momentum fingerprint that is a direct hallmark of the superlattice moiré modification. Third, we reconstruct the wavefunction distribution of the electronic part of the exciton and compare the size with the real-space moiré superlattice. Our work provides direct access to interlayer exciton formation dynamics in space and time and reveals opportunities to study correlated moiré and exciton physics for the future realization of exotic quantum phases of matter.
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28
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Vitalone RA, Sternbach AJ, Foutty BA, McLeod AS, Sow C, Golez D, Nakamura F, Maeno Y, Pasupathy AN, Georges A, Millis AJ, Basov DN. Nanoscale Femtosecond Dynamics of Mott Insulator (Ca 0.99Sr 0.01) 2RuO 4. NANO LETTERS 2022; 22:5689-5697. [PMID: 35839312 DOI: 10.1021/acs.nanolett.2c00581] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Ca2RuO4 is a transition-metal oxide that exhibits a Mott insulator-metal transition (IMT) concurrent with a symmetry-preserving Jahn-Teller distortion (JT) at 350 K. The coincidence of these two transitions demonstrates a high level of coupling between the electronic and structural degrees of freedom in Ca2RuO4. Using spectroscopic measurements with nanoscale spatial resolution, we interrogate the interplay of the JT and IMT through the temperature-driven transition. Then, we introduce photoexcitation with subpicosecond temporal resolution to explore the coupling of the JT and IMT via electron-hole injection under ambient conditions. Through the temperature-driven IMT, we observe phase coexistence in the form of a stripe phase existing at the domain wall between macroscopic insulating and metallic domains. Through ultrafast carrier injection, we observe the formation of midgap states via enhanced optical absorption. We propose that these midgap states become trapped by lattice polarons originating from the local perturbation of the JT.
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Affiliation(s)
- Rocco A Vitalone
- Department of Physics, Columbia University, 1150 Amsterdam Avenue, New York, New York 10027, United States
| | - Aaron J Sternbach
- Department of Physics, Columbia University, 1150 Amsterdam Avenue, New York, New York 10027, United States
| | - Benjamin A Foutty
- Department of Physics, Columbia University, 1150 Amsterdam Avenue, New York, New York 10027, United States
- Department of Physics, Stanford University, 450 Serra Mall, Stanford, California 94305m United States
| | - Alexander S McLeod
- Department of Physics, Columbia University, 1150 Amsterdam Avenue, New York, New York 10027, United States
- School of Physics and Astronomy, University of Minnesota Twin Cities, 115 Union Street SE, Minneapolis, Minnesota 55455, United States
| | - Chanchal Sow
- Deparment of Physics, Kyoto University, Yoshidahonmachi, Sakyo Ward, Kyoto 606-8501, Japan
- Department of Physics, IIT Kanpur, Kalyanpur Kanpur, Uttar Pradesh, India 209016
| | - Denis Golez
- Center for Computational Physics, Flatiron Institute, 162 Fifth Avenue, New York, New York 10010, United States
- Jozef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia
- Faculty of Mathematics and Physics, University of Ljubljana, Jandranska 19, 1000 Ljubljana, Slovenia
| | - Fumihiko Nakamura
- Department of Education and Creation Engineering, Kurume Institute of Technology, Kurume, Fukuoka 830-0052, Japan
| | - Yoshiteru Maeno
- Deparment of Physics, Kyoto University, Yoshidahonmachi, Sakyo Ward, Kyoto 606-8501, Japan
| | - Abhay N Pasupathy
- Department of Physics, Columbia University, 1150 Amsterdam Avenue, New York, New York 10027, United States
| | - Antoine Georges
- Center for Computational Physics, Flatiron Institute, 162 Fifth Avenue, New York, New York 10010, United States
- Department of Physics, College of France, 11Pl. Marcelin, Berthelot, Paris, France FR 75231
- CPHT, CNRS, Polytechnic Institute of Paris, Ecole Polytechnique Palaiseau, Paris, France FR 91128
- DQMP, Universite de Geneve, 24 Quai Ernest Ansermet, Geneve CH-1211, Switzerland
| | - Andrew J Millis
- Department of Physics, Columbia University, 1150 Amsterdam Avenue, New York, New York 10027, United States
- Center for Computational Physics, Flatiron Institute, 162 Fifth Avenue, New York, New York 10010, United States
| | - D N Basov
- Department of Physics, Columbia University, 1150 Amsterdam Avenue, New York, New York 10027, United States
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29
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Karni O, Esin I, Dani KM. Through the Lens of a Momentum Microscope: Viewing Light-Induced Quantum Phenomena in 2D Materials. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022:e2204120. [PMID: 35817468 DOI: 10.1002/adma.202204120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 06/23/2022] [Indexed: 06/15/2023]
Abstract
Van der Waals (vdW) materials at their 2D limit are diverse, flexible, and unique laboratories to study fundamental quantum phenomena and their future applications. Their novel properties rely on their pronounced Coulomb interactions, variety of crystal symmetries and spin-physics, and the ease of incorporation of different vdW materials to form sophisticated heterostructures. In particular, the excited state properties of many 2D semiconductors and semi-metals are relevant for their technological applications, particularly those that can be induced by light. In this paper, the recent advances made in studying out-of-equilibrium, light-induced, phenomena in these materials are reviewed using powerful, surface-sensitive, time-resolved photoemission-based techniques, with a particular emphasis on the emerging multi-dimensional photoemission spectroscopy technique of time-resolved momentum microscopy. The advances this technique has enabled in studying the nature and dynamics of occupied excited states in these materials are discussed. Then, the future research directions opened by these scientific and instrumental advancements are projected for studying the physics of 2D materials and the opportunities to engineer their band-structure and band-topology by laser fields.
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Affiliation(s)
- Ouri Karni
- Department of Applied Physics, Stanford University, Stanford, CA, 94305, USA
- SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA
| | - Iliya Esin
- Department of Physics, California Institute of Technology, Pasadena, CA, 91125, USA
| | - Keshav M Dani
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, 904-0495, Japan
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30
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Liu Y, Elbanna A, Gao W, Pan J, Shen Z, Teng J. Interlayer Excitons in Transition Metal Dichalcogenide Semiconductors for 2D Optoelectronics. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2107138. [PMID: 34700359 DOI: 10.1002/adma.202107138] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Revised: 10/13/2021] [Indexed: 06/13/2023]
Abstract
Optoelectronic materials that allow on-chip integrated light signal emitting, routing, modulation, and detection are crucial for the development of high-speed and high-throughput optical communication and computing technologies. Interlayer excitons in 2D van der Waals heterostructures, where electrons and holes are bounded by Coulomb interaction but spatially localized in different 2D layers, have recently attracted intense attention for their enticing properties and huge potential in device applications. Here, a general view of these 2D-confined hydrogen-like bosonic particles and the state-of-the-art developments with respect to the frontier concepts and prototypes is presented. Staggered type-II band alignment enables expansion of the interlayer direct bandgap from the intrinsic visible in monolayers up to the near- or even mid-infrared spectrum. Owing to large exciton binding energy, together with ultralong lifetime, room-temperature exciton devices and observation of quantum behaviors are demonstrated. With the rapid advances, it can be anticipated that future studies of interlayer excitons will not only allow the construction of all-exciton information processing circuits but will also continue to enrich the panoply of ideas on quantum phenomena.
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Affiliation(s)
- Yuanda Liu
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore, 138634, Singapore
| | - Ahmed Elbanna
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore, 138634, Singapore
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 637371, Singapore
| | - Weibo Gao
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 637371, Singapore
- The Photonics Institute and Center for Disruptive Photonic Technologies, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore
| | - Jisheng Pan
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore, 138634, Singapore
| | - Zexiang Shen
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 637371, Singapore
- The Photonics Institute and Center for Disruptive Photonic Technologies, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore
| | - Jinghua Teng
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore, 138634, Singapore
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31
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Properties of Spatially Indirect Excitons in Nanowire Arrays. APPLIED SCIENCES-BASEL 2022. [DOI: 10.3390/app12104924] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
This paper deals with the excitons formed by electrons and holes located in different, closely placed semiconducting nanowires (spatially indirect excitons). We calculated the charge densities and the binding energies of the excitons for different nanowire diameters D and distances h between the nanowires. Together with the estimated exciton lifetimes, these results suggest that at certain h and D, the spatially indirect excitons in the nanowire arrays may have the potential to serve as information-processing units. Possible ways of exciton generation in the nanowire arrays are discussed.
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32
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Bieniek M, Sadecka K, Szulakowska L, Hawrylak P. Theory of Excitons in Atomically Thin Semiconductors: Tight-Binding Approach. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:1582. [PMID: 35564291 PMCID: PMC9104105 DOI: 10.3390/nano12091582] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/26/2022] [Revised: 04/24/2022] [Accepted: 04/26/2022] [Indexed: 02/01/2023]
Abstract
Atomically thin semiconductors from the transition metal dichalcogenide family are materials in which the optical response is dominated by strongly bound excitonic complexes. Here, we present a theory of excitons in two-dimensional semiconductors using a tight-binding model of the electronic structure. In the first part, we review extensive literature on 2D van der Waals materials, with particular focus on their optical response from both experimental and theoretical points of view. In the second part, we discuss our ab initio calculations of the electronic structure of MoS2, representative of a wide class of materials, and review our minimal tight-binding model, which reproduces low-energy physics around the Fermi level and, at the same time, allows for the understanding of their electronic structure. Next, we describe how electron-hole pair excitations from the mean-field-level ground state are constructed. The electron-electron interactions mix the electron-hole pair excitations, resulting in excitonic wave functions and energies obtained by solving the Bethe-Salpeter equation. This is enabled by the efficient computation of the Coulomb matrix elements optimized for two-dimensional crystals. Next, we discuss non-local screening in various geometries usually used in experiments. We conclude with a discussion of the fine structure and excited excitonic spectra. In particular, we discuss the effect of band nesting on the exciton fine structure; Coulomb interactions; and the topology of the wave functions, screening and dielectric environment. Finally, we follow by adding another layer and discuss excitons in heterostructures built from two-dimensional semiconductors.
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Affiliation(s)
- Maciej Bieniek
- Department of Physics, University of Ottawa, Ottawa, ON K1N 6N5, Canada; (K.S.); (L.S.); (P.H.)
- Department of Theoretical Physics, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
- Institut für Theoretische Physik und Astrophysik, Universität Würzburg, 97074 Würzburg, Germany
| | - Katarzyna Sadecka
- Department of Physics, University of Ottawa, Ottawa, ON K1N 6N5, Canada; (K.S.); (L.S.); (P.H.)
- Department of Theoretical Physics, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
| | - Ludmiła Szulakowska
- Department of Physics, University of Ottawa, Ottawa, ON K1N 6N5, Canada; (K.S.); (L.S.); (P.H.)
| | - Paweł Hawrylak
- Department of Physics, University of Ottawa, Ottawa, ON K1N 6N5, Canada; (K.S.); (L.S.); (P.H.)
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Deng JP, Li HJ, Ma XF, Liu XY, Cui Y, Ma XJ, Li ZQ, Wang ZW. Self-Trapped Interlayer Excitons in van der Waals Heterostructures. J Phys Chem Lett 2022; 13:3732-3739. [PMID: 35445599 DOI: 10.1021/acs.jpclett.2c00565] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The self-trapped state (STS) of the interlayer exciton (IX) has aroused enormous interest owing to its significant impact on the fundamental properties of the van der Waals heterostructures (vdWHs). Nevertheless, the microscopic mechanisms of STS are still controversial. Herein, we study the corrections of the binding energies of the IXs stemming from the exciton-interface optical phonon coupling in four kinds of vdWHs and find that these IXs are in the STS for the appropriate ratio of the electron and hole effective masses. We show that these self-trapped IXs could be classified into type I with the increasing binding energy in the tens of millielectronvolts range, which are very agreement with the red-shift of the IX spectra in experiments, and type II with the decreasing binding energy, which provides a possible explanation for the blue-shift and broad line width of the IX's spectra at low temperatures. Moreover, these two types of exciton states could be transformed into each other by adjusting the structural parameters of vdWHs. These results not only provide an in-depth understanding for the self-trapped mechanism but also shed light on the modulations of IXs in vdWHs.
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Affiliation(s)
- Jia-Pei Deng
- Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparing Technology, Department of Physics, School of Science, Tianjin University, Tianjin 300354, Tianjin, China
| | - Hong-Juan Li
- College of Physics and Intelligent Manufacturing Engineering, Chifeng University, Chifeng 024000, Inner Mongolia, China
| | - Xu-Fei Ma
- Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparing Technology, Department of Physics, School of Science, Tianjin University, Tianjin 300354, Tianjin, China
| | - Xiao-Yi Liu
- Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparing Technology, Department of Physics, School of Science, Tianjin University, Tianjin 300354, Tianjin, China
| | - Yu Cui
- Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparing Technology, Department of Physics, School of Science, Tianjin University, Tianjin 300354, Tianjin, China
| | - Xin-Jun Ma
- Research Team of Extreme Condition Physics, College of Mathematics and Physics, Inner Mongolia Minzu University, Tongliao 028043, Inner Mongolia, China
| | - Zhi-Qing Li
- Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparing Technology, Department of Physics, School of Science, Tianjin University, Tianjin 300354, Tianjin, China
| | - Zi-Wu Wang
- Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparing Technology, Department of Physics, School of Science, Tianjin University, Tianjin 300354, Tianjin, China
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Siday T, Sandner F, Brem S, Zizlsperger M, Perea-Causin R, Schiegl F, Nerreter S, Plankl M, Merkl P, Mooshammer F, Huber MA, Malic E, Huber R. Ultrafast Nanoscopy of High-Density Exciton Phases in WSe 2. NANO LETTERS 2022; 22:2561-2568. [PMID: 35157466 DOI: 10.1021/acs.nanolett.1c04741] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The density-driven transition of an exciton gas into an electron-hole plasma remains a compelling question in condensed matter physics. In two-dimensional transition metal dichalcogenides, strongly bound excitons can undergo this phase change after transient injection of electron-hole pairs. Unfortunately, unavoidable nanoscale inhomogeneity in these materials has impeded quantitative investigation into this elusive transition. Here, we demonstrate how ultrafast polarization nanoscopy can capture the Mott transition through the density-dependent recombination dynamics of electron-hole pairs within a WSe2 homobilayer. For increasing carrier density, an initial monomolecular recombination of optically dark excitons transitions continuously into a bimolecular recombination of an unbound electron-hole plasma above 7 × 1012 cm-2. We resolve how the Mott transition modulates over nanometer length scales, directly evidencing the strong inhomogeneity in stacked monolayers. Our results demonstrate how ultrafast polarization nanoscopy could unveil the interplay of strong electronic correlations and interlayer coupling within a diverse range of stacked and twisted two-dimensional materials.
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Affiliation(s)
- Thomas Siday
- Department of Physics and Regensburg Center for Ultrafast Nanoscopy (RUN), University of Regensburg, 93040 Regensburg, Germany
| | - Fabian Sandner
- Department of Physics and Regensburg Center for Ultrafast Nanoscopy (RUN), University of Regensburg, 93040 Regensburg, Germany
| | - Samuel Brem
- Department of Physics, Philipps-Universität Marburg, 35032 Marburg, Germany
- Department of Physics, Chalmers University of Technology, 41296 Gothenburg, Sweden
| | - Martin Zizlsperger
- Department of Physics and Regensburg Center for Ultrafast Nanoscopy (RUN), University of Regensburg, 93040 Regensburg, Germany
| | - Raul Perea-Causin
- Department of Physics, Chalmers University of Technology, 41296 Gothenburg, Sweden
| | - Felix Schiegl
- Department of Physics and Regensburg Center for Ultrafast Nanoscopy (RUN), University of Regensburg, 93040 Regensburg, Germany
| | - Svenja Nerreter
- Department of Physics and Regensburg Center for Ultrafast Nanoscopy (RUN), University of Regensburg, 93040 Regensburg, Germany
| | - Markus Plankl
- Department of Physics and Regensburg Center for Ultrafast Nanoscopy (RUN), University of Regensburg, 93040 Regensburg, Germany
| | - Philipp Merkl
- Department of Physics and Regensburg Center for Ultrafast Nanoscopy (RUN), University of Regensburg, 93040 Regensburg, Germany
| | - Fabian Mooshammer
- Department of Physics and Regensburg Center for Ultrafast Nanoscopy (RUN), University of Regensburg, 93040 Regensburg, Germany
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Markus A Huber
- Department of Physics and Regensburg Center for Ultrafast Nanoscopy (RUN), University of Regensburg, 93040 Regensburg, Germany
| | - Ermin Malic
- Department of Physics, Philipps-Universität Marburg, 35032 Marburg, Germany
- Department of Physics, Chalmers University of Technology, 41296 Gothenburg, Sweden
| | - Rupert Huber
- Department of Physics and Regensburg Center for Ultrafast Nanoscopy (RUN), University of Regensburg, 93040 Regensburg, Germany
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35
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Zhou H, Sun C, Xin W, Li Y, Chen Y, Zhu H. Spatiotemporally Coupled Electron-Hole Dynamics in Two Dimensional Heterostructures. NANO LETTERS 2022; 22:2547-2553. [PMID: 35285224 DOI: 10.1021/acs.nanolett.2c00479] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Coulomb interactions play a crucial role in low-dimensional semiconductor materials, e.g., 2D layered semiconductors, dictating their electronic and optical properties. However, fundamental questions remain as to whether and how Coulomb interactions affect the charge or energy flow in 2D heterostructures, which is essential for their light-electricity conversions. Herein, using ultrafast spectroscopy, we report real space coupled electron-hole dynamics in 2D heterostructures. We show in (WSe2/)WS2/MoTe2 with a controlled energy gradient for the hole and a near flat band for electron transfer, the fate of the electron is controlled by the hole in coupled dynamics. The interfacial electron transfer from WS2 to MoTe2 follows the hole closely and can be facilitated or suppressed by dynamic Coulomb interaction. In parallel to the band alignment, this study reveals the critical role of Coulomb interactions on the fate of photogenerated charges in 2D heterostructures, providing experimental evidence for coupled electron-hole dynamics and a new knob for steering nanoscale charge or energy transfer process.
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Affiliation(s)
- Hongzhi Zhou
- State Key Laboratory of Modern Optical Instrumentation, Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang 310027, China
| | - Cheng Sun
- State Key Laboratory of Modern Optical Instrumentation, Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang 310027, China
| | - Wei Xin
- Key Laboratory of UV-Emitting Materials and Technology, Ministry of Education, Northeast Normal University, Changchun, Jilin 130024, China
| | - Yujie Li
- State Key Laboratory of Modern Optical Instrumentation, Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang 310027, China
| | - Yuzhong Chen
- State Key Laboratory of Modern Optical Instrumentation, Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang 310027, China
| | - Haiming Zhu
- State Key Laboratory of Modern Optical Instrumentation, Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang 310027, China
- Hangzhou Global Scientific and Technological Innovation Center, Zhejiang University, Hangzhou 310014, P. R. China
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36
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Karmakar A, Al-Mahboob A, Petoukhoff CE, Kravchyna O, Chan NS, Taniguchi T, Watanabe K, Dani KM. Dominating Interlayer Resonant Energy Transfer in Type-II 2D Heterostructure. ACS NANO 2022; 16:3861-3869. [PMID: 35262327 DOI: 10.1021/acsnano.1c08798] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Type-II heterostructures (HSs) are essential components of modern electronic and optoelectronic devices. Earlier studies have found that in type-II transition metal dichalcogenide (TMD) HSs, the dominating carrier relaxation pathway is the interlayer charge transfer (CT) mechanism. Here, this report shows that, in a type-II HS formed between monolayers of MoSe2 and ReS2, nonradiative energy transfer (ET) from higher to lower work function material (ReS2 to MoSe2) dominates over the traditional CT process with and without a charge-blocking interlayer. Without a charge-blocking interlayer, the HS area shows 3.6 times MoSe2 photoluminescence (PL) enhancement as compared to the MoSe2 area alone. In a completely encapsulated sample, the HS PL emission further increases by a factor of 6.4. After completely blocking the CT process, more than 1 order of magnitude higher MoSe2 PL emission was achieved from the HS area. This work reveals that the nature of this ET is truly a resonant effect by showing that in a similar type-II HS formed by ReS2 and WSe2, CT dominates over ET, resulting in a severely quenched WSe2 PL. This study not only provides significant insight into the competing interlayer processes but also shows an innovative way to increase the PL emission intensity of the desired TMD material using the ET process by carefully choosing the right material combination for HS.
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Affiliation(s)
- Arka Karmakar
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna, Kunigami District, Okinawa 904-0495, Japan
| | - Abdullah Al-Mahboob
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna, Kunigami District, Okinawa 904-0495, Japan
| | - Christopher E Petoukhoff
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna, Kunigami District, Okinawa 904-0495, Japan
| | - Oksana Kravchyna
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna, Kunigami District, Okinawa 904-0495, Japan
| | - Nicholas S Chan
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna, Kunigami District, Okinawa 904-0495, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - Keshav M Dani
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna, Kunigami District, Okinawa 904-0495, Japan
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37
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Ye T, Li Y, Li J, Shen H, Ren J, Ning CZ, Li D. Nonvolatile electrical switching of optical and valleytronic properties of interlayer excitons. LIGHT, SCIENCE & APPLICATIONS 2022; 11:23. [PMID: 35075106 PMCID: PMC8786835 DOI: 10.1038/s41377-022-00718-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Revised: 01/07/2022] [Accepted: 01/12/2022] [Indexed: 05/10/2023]
Abstract
Long-lived interlayer excitons (IXs) in van der Waals heterostructures (HSs) stacked by monolayer transition metal dichalcogenides (TMDs) carry valley-polarized information and thus could find promising applications in valleytronic devices. Current manipulation approaches for valley polarization of IXs are mainly limited in electrical field/doping, magnetic field or twist-angle engineering. Here, we demonstrate an electrochemical-doping method, which is efficient, in-situ and nonvolatile. We find the emission characteristics of IXs in WS2/WSe2 HSs exhibit a large excitonic/valley-polarized hysteresis upon cyclic-voltage sweeping, which is ascribed to the chemical-doping of O2/H2O redox couple trapped between WSe2 and substrate. Taking advantage of the large hysteresis, a nonvolatile valley-addressable memory is successfully demonstrated. The valley-polarized information can be non-volatilely switched by electrical gating with retention time exceeding 60 min. These findings open up an avenue for nonvolatile valley-addressable memory and could stimulate more investigations on valleytronic devices.
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Affiliation(s)
- Tong Ye
- School of Optical and Electronic Information, Huazhong University of Science and Technology, 430074, Wuhan, China
| | - Yongzhuo Li
- Department of Electronic Engineering, Tsinghua University, 100084, Beijing, China
- Frontier Science Center for Quantum Information, 100084, Beijing, China
| | - Junze Li
- School of Optical and Electronic Information, Huazhong University of Science and Technology, 430074, Wuhan, China
| | - Hongzhi Shen
- School of Optical and Electronic Information, Huazhong University of Science and Technology, 430074, Wuhan, China
| | - Junwen Ren
- School of Optical and Electronic Information, Huazhong University of Science and Technology, 430074, Wuhan, China
| | - Cun-Zheng Ning
- Department of Electronic Engineering, Tsinghua University, 100084, Beijing, China
- Frontier Science Center for Quantum Information, 100084, Beijing, China
- School of Electrical, Computer, and Energy Engineering, Arizona State University, Tempe, AZ, 85287, USA
| | - Dehui Li
- School of Optical and Electronic Information, Huazhong University of Science and Technology, 430074, Wuhan, China.
- Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, 430074, Wuhan, China.
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38
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Abstract
Advances over the past decade have presented new avenues to achieve control over material properties using intense pulses of electromagnetic radiation, with frequencies ranging from optical (approximately 1 PHz, or 1015 Hz) down to below 1 THz (1012 Hz). Some of these new developments have arisen from new experimental methods to drive and observe transient material properties, while others have emerged from new computational techniques that have made nonequilibrium dynamics more tractable to our understanding. One common issue with most attempts to realize control using electromagnetic pulses is the dissipation of energy, which in many cases poses a limit due to uncontrolled heating and has led to strong interest in using lower frequency and/or highly specific excitations to minimize this effect. Emergent developments in experimental tools using shaped X-ray pulses may in the future offer new possibilities for material control, provided that the issue of heat dissipation can be resolved for higher frequency light. The concept of using appropriately shaped pulses of light to control the properties of materials has a range of potential applications, and relies on an understanding of intricate couplings within the material.![]()
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Affiliation(s)
- Steven L Johnson
- Institute for Quantum Electronics, ETH Zürich, Auguste-Piccard-Hof 1, 8093 Zürich, Switzerland.
- SwissFEL, Paul Scherrer Institute, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
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39
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Ab initio Nonadiabatic Dynamics of Semiconductor Nanomaterials via Surface Hopping Method. CHINESE J CHEM PHYS 2022. [DOI: 10.1063/1674-0068/cjcp2111247] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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40
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Krause R, Aeschlimann S, Chávez-Cervantes M, Perea-Causin R, Brem S, Malic E, Forti S, Fabbri F, Coletti C, Gierz I. Microscopic Understanding of Ultrafast Charge Transfer in van der Waals Heterostructures. PHYSICAL REVIEW LETTERS 2021; 127:276401. [PMID: 35061410 DOI: 10.1103/physrevlett.127.276401] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Revised: 09/29/2021] [Accepted: 11/12/2021] [Indexed: 06/14/2023]
Abstract
Van der Waals heterostructures show many intriguing phenomena including ultrafast charge separation following strong excitonic absorption in the visible spectral range. However, despite the enormous potential for future applications in the field of optoelectronics, the underlying microscopic mechanism remains controversial. Here we use time- and angle-resolved photoemission spectroscopy combined with microscopic many-particle theory to reveal the relevant microscopic charge transfer channels in epitaxial WS_{2}/graphene heterostructures. We find that the timescale for efficient ultrafast charge separation in the material is determined by direct tunneling at those points in the Brillouin zone where WS_{2} and graphene bands cross, while the lifetime of the charge separated transient state is set by defect-assisted tunneling through localized sulphur vacancies. The subtle interplay of intrinsic and defect-related charge transfer channels revealed in the present work can be exploited for the design of highly efficient light harvesting and detecting devices.
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Affiliation(s)
- R Krause
- University of Regensburg, Institute for Experimental and Applied Physics, 93040 Regensburg, Germany
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, 22761 Hamburg, Germany
| | - S Aeschlimann
- University of Regensburg, Institute for Experimental and Applied Physics, 93040 Regensburg, Germany
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, 22761 Hamburg, Germany
| | - M Chávez-Cervantes
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, 22761 Hamburg, Germany
| | - R Perea-Causin
- Chalmers University of Technology, Department of Physics, 41296 Gothenburg, Sweden
| | - S Brem
- Philipps-Universität Marburg, Department of Physics, 35032 Marburg, Germany
| | - E Malic
- Chalmers University of Technology, Department of Physics, 41296 Gothenburg, Sweden
- Philipps-Universität Marburg, Department of Physics, 35032 Marburg, Germany
| | - S Forti
- Center for Nanotechnology Innovation at NEST, Istituto Italiano di Tecnologia, 56127 Pisa, Italy
| | - F Fabbri
- Center for Nanotechnology Innovation at NEST, Istituto Italiano di Tecnologia, 56127 Pisa, Italy
- NEST, Istituto Nanoscienze, CNR and Scuola Normale Superiore, 56127 Pisa, Italy
- Graphene Labs, Istituto Italiano di Tecnologia, 16163 Genova, Italy
| | - C Coletti
- Center for Nanotechnology Innovation at NEST, Istituto Italiano di Tecnologia, 56127 Pisa, Italy
- Graphene Labs, Istituto Italiano di Tecnologia, 16163 Genova, Italy
| | - I Gierz
- University of Regensburg, Institute for Experimental and Applied Physics, 93040 Regensburg, Germany
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41
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Rosati R, Wagner K, Brem S, Perea-Causín R, Ziegler JD, Zipfel J, Taniguchi T, Watanabe K, Chernikov A, Malic E. Non-equilibrium diffusion of dark excitons in atomically thin semiconductors. NANOSCALE 2021; 13:19966-19972. [PMID: 34821228 DOI: 10.1039/d1nr06230a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Atomically thin semiconductors provide an excellent platform to study intriguing many-particle physics of tightly-bound excitons. In particular, the properties of tungsten-based transition metal dichalcogenides are determined by a complex manifold of bright and dark exciton states. While dark excitons are known to dominate the relaxation dynamics and low-temperature photoluminescence, their impact on the spatial propagation of excitons has remained elusive. In our joint theory-experiment study, we address this intriguing regime of dark state transport by resolving the spatio-temporal exciton dynamics in hBN-encapsulated WSe2 monolayers after resonant excitation. We find clear evidence of an unconventional, time-dependent diffusion during the first tens of picoseconds, exhibiting strong deviation from the steady-state propagation. Dark exciton states are initially populated by phonon emission from the bright states, resulting in creation of hot (unequilibrated) excitons whose rapid expansion leads to a transient increase of the diffusion coefficient by more than one order of magnitude. These findings are relevant for both fundamental understanding of the spatio-temporal exciton dynamics in atomically thin materials as well as their technological application by enabling rapid diffusion.
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Affiliation(s)
- Roberto Rosati
- Department of Physics, Philipps-Universität Marburg, Renthof 7, D-35032 Marburg, Germany.
| | - Koloman Wagner
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062 Dresden, Germany
| | - Samuel Brem
- Department of Physics, Philipps-Universität Marburg, Renthof 7, D-35032 Marburg, Germany.
| | - Raül Perea-Causín
- Chalmers University of Technology, Department of Physics, 412 96 Gothenburg, Sweden
| | - Jonas D Ziegler
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062 Dresden, Germany
| | - Jonas Zipfel
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Ibaraki 305-004, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Ibaraki 305-004, Japan
| | - Alexey Chernikov
- Department of Physics, University of Regensburg, Regensburg D-93053, Germany
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062 Dresden, Germany
| | - Ermin Malic
- Department of Physics, Philipps-Universität Marburg, Renthof 7, D-35032 Marburg, Germany.
- Chalmers University of Technology, Department of Physics, 412 96 Gothenburg, Sweden
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42
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Rosati R, Schmidt R, Brem S, Perea-Causín R, Niehues I, Kern J, Preuß JA, Schneider R, Michaelis de Vasconcellos S, Bratschitsch R, Malic E. Dark exciton anti-funneling in atomically thin semiconductors. Nat Commun 2021; 12:7221. [PMID: 34893602 PMCID: PMC8664915 DOI: 10.1038/s41467-021-27425-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Accepted: 11/16/2021] [Indexed: 11/09/2022] Open
Abstract
Transport of charge carriers is at the heart of current nanoelectronics. In conventional materials, electronic transport can be controlled by applying electric fields. Atomically thin semiconductors, however, are governed by excitons, which are neutral electron-hole pairs and as such cannot be controlled by electrical fields. Recently, strain engineering has been introduced to manipulate exciton propagation. Strain-induced energy gradients give rise to exciton funneling up to a micrometer range. Here, we combine spatiotemporal photoluminescence measurements with microscopic theory to track the way of excitons in time, space and energy. We find that excitons surprisingly move away from high-strain regions. This anti-funneling behavior can be ascribed to dark excitons which possess an opposite strain-induced energy variation compared to bright excitons. Our findings open new possibilities to control transport in exciton-dominated materials. Overall, our work represents a major advance in understanding exciton transport that is crucial for technological applications of atomically thin materials.
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Affiliation(s)
- Roberto Rosati
- Department of Physics, Philipps-Universität Marburg, 35032, Marburg, Germany
| | - Robert Schmidt
- Institute of Physics and Center for Nanotechnology, University of Münster, 48149, Münster, Germany
| | - Samuel Brem
- Department of Physics, Philipps-Universität Marburg, 35032, Marburg, Germany
| | - Raül Perea-Causín
- Chalmers University of Technology, Department of Physics, 412 96, Gothenburg, Sweden
| | - Iris Niehues
- Institute of Physics and Center for Nanotechnology, University of Münster, 48149, Münster, Germany
| | - Johannes Kern
- Institute of Physics and Center for Nanotechnology, University of Münster, 48149, Münster, Germany
| | - Johann A Preuß
- Institute of Physics and Center for Nanotechnology, University of Münster, 48149, Münster, Germany
| | - Robert Schneider
- Institute of Physics and Center for Nanotechnology, University of Münster, 48149, Münster, Germany
| | | | - Rudolf Bratschitsch
- Institute of Physics and Center for Nanotechnology, University of Münster, 48149, Münster, Germany.
| | - Ermin Malic
- Department of Physics, Philipps-Universität Marburg, 35032, Marburg, Germany.
- Chalmers University of Technology, Department of Physics, 412 96, Gothenburg, Sweden.
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43
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Tran TN, Kim S, White SJU, Nguyen MAP, Xiao L, Strauf S, Yang T, Aharonovich I, Xu ZQ. Enhanced Emission from Interlayer Excitons Coupled to Plasmonic Gap Cavities. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2021; 17:e2103994. [PMID: 34605163 DOI: 10.1002/smll.202103994] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Revised: 08/31/2021] [Indexed: 06/13/2023]
Abstract
The emergence of interlayer excitons (IEs) from atomic layered transition metal dichalcogenides (TMDCs) heterostructures has drawn tremendous attention due to their unique and exotic optoelectronic properties. Coupling the IEs into optical cavities provides distinctive electromagnetic environments which plays an important role in controlling multiple optical processes such as optical nonlinear generation or photoluminescence enhancement. Here, the integration of IEs in TMDCs into plasmonic nanocavities based on a nanocube on a metallic mirror is reported. Spectroscopic studies reveal an order of magnitude enhancement of the IE at room temperature and a 5-time enhancement in fluorescence at cryogenic temperatures. Cavity modeling reveals that the enhancement of the emission is attributed to both increased excitation efficiency and Purcell effect from the cavity. The results show a novel method to control the excitonic processes in TMDC heterostructures to build high performance photonics and optoelectronics devices.
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Affiliation(s)
- Thinh N Tran
- School of Mathematical and Physical Sciences, University of Technology Sydney, Ultimo, New South Wales, 2007, Australia
| | - Sejeong Kim
- Department of Electrical and Electronic Engineering, Faculty of Engineering and Information Technology, University of Melbourne, Victoria, 3010, Australia
| | - Simon J U White
- School of Mathematical and Physical Sciences, University of Technology Sydney, Ultimo, New South Wales, 2007, Australia
| | - Minh Anh Phan Nguyen
- School of Mathematical and Physical Sciences, University of Technology Sydney, Ultimo, New South Wales, 2007, Australia
| | - Licheng Xiao
- Department of Physics, Stevens Institute of Technology, Hoboken, New Jersey, 07030, USA
- Center for Quantum Science and Engineering, Stevens Institute of Technology, Hoboken, New Jersey, 07030, USA
| | - Stefan Strauf
- Department of Physics, Stevens Institute of Technology, Hoboken, New Jersey, 07030, USA
- Center for Quantum Science and Engineering, Stevens Institute of Technology, Hoboken, New Jersey, 07030, USA
| | - Tieshan Yang
- School of Mathematical and Physical Sciences, University of Technology Sydney, Ultimo, New South Wales, 2007, Australia
- ARC Centre of Excellence for Transformative Meta-Optical Systems (TMOS), University of Technology Sydney, Ultimo, New South Wales, 2007, Australia
| | - Igor Aharonovich
- School of Mathematical and Physical Sciences, University of Technology Sydney, Ultimo, New South Wales, 2007, Australia
- ARC Centre of Excellence for Transformative Meta-Optical Systems (TMOS), University of Technology Sydney, Ultimo, New South Wales, 2007, Australia
| | - Zai-Quan Xu
- School of Mathematical and Physical Sciences, University of Technology Sydney, Ultimo, New South Wales, 2007, Australia
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44
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Yang J, Jiang S, Xie J, Jiang H, Xu S, Zhang K, Shi Y, Zhang Y, Zeng Z, Fang G, Wang T, Su F. Identifying the Intermediate Free-Carrier Dynamics Across the Charge Separation in Monolayer MoS 2/ReSe 2 Heterostructures. ACS NANO 2021; 15:16760-16768. [PMID: 34549939 DOI: 10.1021/acsnano.1c06822] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Van der Waals heterostructures composed of different two-dimensional films offer a unique platform for engineering and promoting photoelectric performances, which highly demands the understanding of photocarrier dynamics. Herein, large-scale vertically stacked heterostructures with MoS2 and ReSe2 monolayers are fabricated. Correspondingly, the carrier dynamics have been thoroughly investigated using different ultrafast spectroscopies, including Terahertz (THz) emission spectroscopy, time-resolved THz spectroscopy (TRTS), and near-infrared optical pump-probe spectroscopy (OPPS), providing complementary dynamic information for the out-of-plane charge separation and in-plane charge transport at different stages. The initial charge transfer (CT) within the first 170 fs, generating a transient directional current, is directly demonstrated by the THz emissions. Furthermore, the TRTS explicitly unveils an intermediate free-carrier relaxation pathway, featuring a pronounced augmentation of THz photoconductivity compared to the isolated ReSe2 layer, which likely contains the evolution from immigrant hot charged free carriers to bounded interlayer excitons (∼0.7 ps) and the surface defect trapping (∼13 ps). In addition, the OPPS reveals a distinct enhancement in the saturable absorption along with long-lived dynamics (∼365 ps), which originated from the CT and interlayer exciton recombination. Our work provides comprehensive insight into the photocarrier dynamics across the charge separation and will help with the development of optoelectronic devices based on ReSe2-MoS2 heterostructures.
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Affiliation(s)
- Jin Yang
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, China
- University of Science and Technology of China, Hefei 230026, China
| | - Shaolong Jiang
- Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
| | - Jiafeng Xie
- GBA branch of Aerospace Information Research Institute, Chinese Academy of Sciences, Guangzhou 510700, China
| | - Huachao Jiang
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, China
| | - Shujuan Xu
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, China
- University of Science and Technology of China, Hefei 230026, China
| | - Kai Zhang
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, China
| | - Yuping Shi
- Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, China
| | - Yanfeng Zhang
- Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, China
| | - Zhi Zeng
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, China
| | - Guangyou Fang
- GBA branch of Aerospace Information Research Institute, Chinese Academy of Sciences, Guangzhou 510700, China
| | - Tianwu Wang
- GBA branch of Aerospace Information Research Institute, Chinese Academy of Sciences, Guangzhou 510700, China
| | - Fuhai Su
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, China
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45
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Zimmermann JE, Axt M, Mooshammer F, Nagler P, Schüller C, Korn T, Höfer U, Mette G. Ultrafast Charge-Transfer Dynamics in Twisted MoS 2/WSe 2 Heterostructures. ACS NANO 2021; 15:14725-14731. [PMID: 34520661 DOI: 10.1021/acsnano.1c04549] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Two-dimensional transition metal dichalcogenides offer a fascinating platform for creating van der Waals heterojunctions with exciting physical properties. Because of their typical type-II band alignment, photoexcited electrons and holes can separate via interfacial charge transfer. Furthermore, the relative crystallographic alignment of the individual layers in these heterostructures represents an important degree of freedom. Based on both effects, various fascinating ideas for applications in optoelectronics and valleytronics have been suggested. Despite its utmost importance for the design and efficiency of potential devices, the nature and the dynamics of ultrafast charge transfer are not yet well understood. This is mainly because the charge transfer can be surprisingly fast, usually faster than the temporal resolution of previous experimental approaches. Here, we apply time- and polarization-resolved second-harmonic imaging microscopy to investigate the charge-transfer dynamics for three MoS2/WSe2 heterostructures with different stacking angles at a previously unattainable time resolution of ≈10 fs. For 1.70 eV excitation energy, electron transfer from WSe2 to MoS2 is found to depend considerably on the stacking angle with the fastest transfer time observed to be as short as 12 fs. At 1.85 eV excitation energy, ultrafast hole transfer from MoS2 to hybridized states at the Γ-point and to the K-points of WSe2 has to be considered. Surprisingly, the corresponding decay dynamics show only a minor stacking-angle dependence indicating that radiative recombination of momentum-space indirect Γ-K excitons becomes the dominant decay route for all samples.
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Affiliation(s)
- Jonas E Zimmermann
- Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität, 35032 Marburg, Germany
| | - Marleen Axt
- Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität, 35032 Marburg, Germany
| | - Fabian Mooshammer
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg, 93053 Regensburg, Germany
| | - Philipp Nagler
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg, 93053 Regensburg, Germany
| | - Christian Schüller
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg, 93053 Regensburg, Germany
| | - Tobias Korn
- Institut für Physik, Universität Rostock, 18059 Rostock, Germany
| | - Ulrich Höfer
- Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität, 35032 Marburg, Germany
| | - Gerson Mette
- Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität, 35032 Marburg, Germany
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46
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Zhang C, Zhang Y, Fang Z, Chen Y, Chen Z, He H, Zhu H. Near-Unity-Efficiency Energy Transfer from Perovskite to Monolayer Semiconductor through Long-Range Migration and Asymmetric Interfacial Transfer. ACS APPLIED MATERIALS & INTERFACES 2021; 13:41895-41903. [PMID: 34432427 DOI: 10.1021/acsami.1c11753] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
van der Waals heterostructures combining perovskites of strong light absorption with atomically thin two-dimensional (2D) transition-metal dichalcogenides (TMDs) hold great potential for light-harvesting and optoelectronic applications. However, current research studies integrating TMDs with low-dimensional perovskite nanomaterials generally suffer from poor carrier/energy transport and harnessing, stemming from poor interfacial interaction due to the nanostructured nature and ligands on surface/interface. To overcome the limitations, here, we report prototypical three-dimensional (3D)/2D perovskite/TMD heterostructures by combing highly smooth and ligand-free CsPbBr3 film with a WSe2 monolayer. We show that the energy transfer at interface occurs through asymmetric two-step charge-transfer process, with ultrafast hole transfer in ∼200 fs and subsequent electron transfer in ∼10 ps, driven by the asymmetric type I band alignment. The energy migration and transfer from CsPbBr3 film to WSe2 can be well described by a one-dimensional diffusion model with a carrier diffusion length of ∼500 nm in CsPbBr3 film. Thanks to the long-range carrier migration and ultrafast interfacial transfer, highly efficient (>90%) energy transfer to WSe2 can be achieved with CsPbBr3 film as thick as ∼180 nm, which can capture most of the light above its band gap. The efficient light and energy harvesting in perovskite/TMD 3D/2D heterostructures suggest great promise in optoelectronic and photonic devices.
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Affiliation(s)
- Chi Zhang
- State Key Laboratory of Modern Optical Instrumentation, Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou 310027, Zhejiang, China
| | - Yao Zhang
- State Key Laboratory of Modern Optical Instrumentation, Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou 310027, Zhejiang, China
| | - Zhishan Fang
- State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, Zhejiang, China
| | - Yuzhong Chen
- State Key Laboratory of Modern Optical Instrumentation, Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou 310027, Zhejiang, China
| | - Zeng Chen
- State Key Laboratory of Modern Optical Instrumentation, Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou 310027, Zhejiang, China
| | - Haiping He
- State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, Zhejiang, China
| | - Haiming Zhu
- State Key Laboratory of Modern Optical Instrumentation, Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou 310027, Zhejiang, China
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47
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Niu X, Xiao S, Sun D, Shi A, Zhou Z, Chen W, Li X, Wang J. Direct formation of interlayer exciton in two-dimensional van der Waals heterostructures. MATERIALS HORIZONS 2021; 8:2208-2215. [PMID: 34846425 DOI: 10.1039/d1mh00571e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
In atomically thin two-dimensional van der Waals (2D vdW) heterostructures, spatially separated interlayer excitons play an important role in the optoelectronic performance and show great potential for the exploration of many-body quantum phenomena. A commonly accepted formation mode for interlayer excitons is via a two-step intralayer exciton transfer mechanism, namely, photo-excited intralayer excitons are initially generated in individual sublayers, and photogenerated electrons and holes are then separated into opposite sublayers based on the type-II band alignment. Herein, we expand the concept of interlayer exciton formation and reveal that bright interlayer excitons can be generated in one step by direct interlayer photoexcitation in 2D vdW heterostructures that have strong interlayer coupling and a short photoexcitation channel. First-principles and many-body perturbation theory calculations demonstrate that indium selenide/antimonene and indium selenide/black phosphorus heterostructures are two promising systems that show an exceptionally large interlayer transition probability (>500 Debye2). This study enriches the understanding of interlayer exciton formation and provides a new avenue to acquiring strong interlayer excitons in artificial 2D vdW heterostructures.
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Affiliation(s)
- Xianghong Niu
- New Energy Technology Engineering Laboratory of Jiangsu Province & School of Science, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
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48
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Wu K, Zhong H, Guo Q, Tang J, Zhang J, Qian L, Shi Z, Zhang C, Yuan S, Zhang S, Xu H. Identification of twist-angle-dependent excitons in WS2/WSe2 heterobilayers. Natl Sci Rev 2021; 9:nwab135. [PMID: 35795458 PMCID: PMC9252742 DOI: 10.1093/nsr/nwab135] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2020] [Revised: 06/30/2021] [Accepted: 07/12/2021] [Indexed: 11/13/2022] Open
Abstract
Abstract
Stacking atomically thin films enables artificial construction of van der Waals heterostructures with exotic functionalities such as superconductivity, the quantum Hall effect, and engineered light-matter interactions. In particular, heterobilayers composed of monolayer transition metal dichalcogenides have attracted significant interest due to their controllable interlayer coupling and trapped valley excitons in moiré superlattices. However, the identification of twist-angle-modulated optical transitions in heterobilayers is sometimes controversial since both momentum-direct (K-K) and -indirect excitons reside on the low energy side of the bright exciton in the monolayer constituents. Here, we attribute the optical transition at approximately 1.35 eV in the WS2/WSe2 heterobilayer to an indirect Γ-K transition based on a systematic analysis and comparison of experimental PL spectra with theoretical calculations. The exciton wavefunction obtained by the state-of-the-art GW-Bethe-Salpeter equation (GW-BSE) approach indicates that both the electron and hole of the exciton are contributed by the WS2 layer. Polarization-resolved k-space imaging further confirms that the transition dipole moment of this optical transition is dominantly in-plane and is independent of the twist angle. The calculated absorption spectrum predicts that the usually called interlayer exciton peak coming from the K-K transition is located at 1.06 eV, but with a much weaker amplitude. Our work provides new insights into understanding the steady-state and dynamic properties of twist-angle-dependent excitons in van der Waals heterostructures.
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Affiliation(s)
- Ke Wu
- School of Physics and Technology and Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Wuhan University, Wuhan 430072, China
- School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Hongxia Zhong
- School of Physics and Technology and Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Wuhan University, Wuhan 430072, China
| | - Quanbing Guo
- School of Physics and Technology and Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Wuhan University, Wuhan 430072, China
| | - Jibo Tang
- The Institute for Advanced Studies, Wuhan University, Wuhan 430072, China
| | - Jing Zhang
- School of Physics and Technology and Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Wuhan University, Wuhan 430072, China
| | - Lihua Qian
- School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Zhifeng Shi
- Key Laboratory of Materials Physics of Ministry of Education, School of Physics and Microelectronics, Zhengzhou University, Zhengzhou 450052, China
| | - Chendong Zhang
- School of Physics and Technology and Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Wuhan University, Wuhan 430072, China
| | - Shengjun Yuan
- School of Physics and Technology and Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Wuhan University, Wuhan 430072, China
| | - Shunping Zhang
- School of Physics and Technology and Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Wuhan University, Wuhan 430072, China
| | - Hongxing Xu
- School of Physics and Technology and Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Wuhan University, Wuhan 430072, China
- The Institute for Advanced Studies, Wuhan University, Wuhan 430072, China
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49
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Wallauer R, Perea-Causin R, Münster L, Zajusch S, Brem S, Güdde J, Tanimura K, Lin KQ, Huber R, Malic E, Höfer U. Momentum-Resolved Observation of Exciton Formation Dynamics in Monolayer WS 2. NANO LETTERS 2021; 21:5867-5873. [PMID: 34165994 DOI: 10.1021/acs.nanolett.1c01839] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The dynamics of momentum-dark exciton formation in transition metal dichalcogenides is difficult to measure experimentally, as many momentum-indirect exciton states are not accessible to optical interband spectroscopy. Here, we combine a tunable pump, high-harmonic probe laser source with a 3D momentum imaging technique to map photoemitted electrons from monolayer WS2. This provides momentum-, energy- and time-resolved access to excited states on an ultrafast time scale. The high temporal resolution of the setup allows us to trace the early-stage exciton dynamics on its intrinsic time scale and observe the formation of a momentum-forbidden dark KΣ exciton a few tens of femtoseconds after optical excitation. By tuning the excitation energy, we manipulate the temporal evolution of the coherent excitonic polarization and observe its influence on the dark exciton formation. The experimental results are in excellent agreement with a fully microscopic theory, resolving the temporal and spectral dynamics of bright and dark excitons in WS2.
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Affiliation(s)
- Robert Wallauer
- Fachbereich Physik, Philipps-Universität, Marburg 35032, Germany
| | - Raul Perea-Causin
- Department of Physics, Chalmers University of Technology, Gothenburg SE-412 96, Sweden
| | - Lasse Münster
- Fachbereich Physik, Philipps-Universität, Marburg 35032, Germany
| | - Sarah Zajusch
- Fachbereich Physik, Philipps-Universität, Marburg 35032, Germany
| | - Samuel Brem
- Fachbereich Physik, Philipps-Universität, Marburg 35032, Germany
| | - Jens Güdde
- Fachbereich Physik, Philipps-Universität, Marburg 35032, Germany
| | - Katsumi Tanimura
- The Institute of Scientific and Industrial Research, Osaka University, Osaka 5670047, Japan
| | - Kai-Qiang Lin
- Department of Physics, University of Regensburg, Regensburg 93040, Germany
| | - Rupert Huber
- Department of Physics, University of Regensburg, Regensburg 93040, Germany
| | - Ermin Malic
- Fachbereich Physik, Philipps-Universität, Marburg 35032, Germany
- Department of Physics, Chalmers University of Technology, Gothenburg SE-412 96, Sweden
| | - Ulrich Höfer
- Fachbereich Physik, Philipps-Universität, Marburg 35032, Germany
- Zentrum für Materialwissenschaften, Philipps-Universität, Marburg 35032, Germany
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50
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Abstract
Interlayer excitons in van der Waals heterostructures have tunable electron-hole separation in both real space and momentum space, enabling unprecedented control over excitonic properties to be exploited in a wide array of future applications ranging from exciton condensation to valleytronic and optoelectronic devices.
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Affiliation(s)
- Kai-Qiang Lin
- Department of Physics, University of Regensburg, Regensburg, Germany.
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