1
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Sui Y, Cheng X, Liu Q, Tang Y, Xu Z, Wei K. High-order exciton complexes induced by an interlayer carrier transfer in 2D van der Waals heterostructures. OPTICS LETTERS 2024; 49:161-164. [PMID: 38134177 DOI: 10.1364/ol.507084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Accepted: 11/14/2023] [Indexed: 12/24/2023]
Abstract
High-order correlated excitonic states, such as biexciton, charged biexciton, and polaron, hold a promising platform in contemporary quantum and nonlinear optics due to their large Bohr radii and thus strong nonlinear interactions. The recently found 2D TMDs further give such excitonic states additional valley properties, with bound state of excitons in opposite valleys in momentum spaces. Despite great efforts that have been made on emission properties of excitonic states, their absorption features, especially the ultrafast absorption dynamics, are rarely reported. Here, we reported the enhanced optical absorption of the high-order charged-excitonic states in monolayer WS2, including singlet, triplet, and semidark trions (3-particle state), and charged biexcitons (5-particle state), by utilizing the interlayer charge transfer-induced photo-doping effect in the graphene-WS2 heterostructure. Depending on recombination rates of doping electrons, absorption intensities of charged complexes exhibit ultrafast decay dynamics, with lifetimes of several picoseconds. Due to many-body interaction, both increasing pump intensity and lattice temperature can broaden these fine excitonic absorption peaks and even reverse the shape of the transient absorption spectrum.
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2
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Adler ER, Le TDM, Boulares I, Boyd R, He Y, Rhodes D, Van Keuren E, Barbara P, Najmaei S. Observation of Multi-Phonon Emission in Monolayer WS 2 on Various Substrates. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 14:37. [PMID: 38202492 PMCID: PMC10780943 DOI: 10.3390/nano14010037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Revised: 12/14/2023] [Accepted: 12/19/2023] [Indexed: 01/12/2024]
Abstract
Transition metal dichalcogenides (TMDs) have unique absorption and emission properties that stem from their large excitonic binding energies, reduced-dielectric screening, and strong spin-orbit coupling. However, the role of substrates, phonons, and material defects in the excitonic scattering processes remains elusive. In tungsten-based TMDs, it is known that the excitons formed from electrons in the lower-energy conduction bands are dark in nature, whereas low-energy emissions in the photoluminescence spectrum have been linked to the brightening of these transitions, either via defect scattering or via phonon scattering with first-order phonon replicas. Through temperature and incident-power-dependent studies of WS2 grown by CVD or exfoliated from high-purity bulk crystal on different substrates, we demonstrate that the strong exciton-phonon coupling yields brightening of dark transitions up to sixth-order phonon replicas. We discuss the critical role of defects in the brightening pathways of dark excitons and their phonon replicas, and we elucidate that these emissions are intrinsic to the material and independent of substrate, encapsulation, growth method, and transfer approach.
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Affiliation(s)
- Eli R. Adler
- Department of Physics, Georgetown University, Washington, DC 20057, USA; (E.R.A.); (T.D.M.L.); (E.V.K.)
- U.S. Army Combat Capabilities Development Command, Army Research Laboratory, Adelphi, MD 20783, USA
| | - Thy Doan Mai Le
- Department of Physics, Georgetown University, Washington, DC 20057, USA; (E.R.A.); (T.D.M.L.); (E.V.K.)
| | - Ibrahim Boulares
- U.S. Army Combat Capabilities Development Command, Army Research Laboratory, Adelphi, MD 20783, USA
| | - Robert Boyd
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Yangchen He
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Daniel Rhodes
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Edward Van Keuren
- Department of Physics, Georgetown University, Washington, DC 20057, USA; (E.R.A.); (T.D.M.L.); (E.V.K.)
| | - Paola Barbara
- Department of Physics, Georgetown University, Washington, DC 20057, USA; (E.R.A.); (T.D.M.L.); (E.V.K.)
| | - Sina Najmaei
- U.S. Army Combat Capabilities Development Command, Army Research Laboratory, Adelphi, MD 20783, USA
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3
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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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4
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Chand SB, Woods JM, Quan J, Mejia E, Taniguchi T, Watanabe K, Alù A, Grosso G. Interaction-driven transport of dark excitons in 2D semiconductors with phonon-mediated optical readout. Nat Commun 2023; 14:3712. [PMID: 37349290 DOI: 10.1038/s41467-023-39339-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Accepted: 06/08/2023] [Indexed: 06/24/2023] Open
Abstract
The growing field of quantum information technology requires propagation of information over long distances with efficient readout mechanisms. Excitonic quantum fluids have emerged as a powerful platform for this task due to their straightforward electro-optical conversion. In two-dimensional transition metal dichalcogenides, the coupling between spin and valley provides exciting opportunities for harnessing, manipulating, and storing bits of information. However, the large inhomogeneity of single layers cannot be overcome by the properties of bright excitons, hindering spin-valley transport. Nonetheless, the rich band structure supports dark excitonic states with strong binding energy and longer lifetime, ideally suited for long-range transport. Here we show that dark excitons can diffuse over several micrometers and prove that this repulsion-driven propagation is robust across non-uniform samples. The long-range propagation of dark states with an optical readout mediated by chiral phonons provides a new concept of excitonic devices for applications in both classical and quantum information technology.
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Affiliation(s)
- Saroj B Chand
- Photonics Initiative, Advanced Science Research Center, City University of New York, New York, NY, 10031, USA
| | - John M Woods
- Photonics Initiative, Advanced Science Research Center, City University of New York, New York, NY, 10031, USA
| | - Jiamin Quan
- Photonics Initiative, Advanced Science Research Center, City University of New York, New York, NY, 10031, USA
| | - Enrique Mejia
- Photonics Initiative, Advanced Science Research Center, City University of New York, New York, NY, 10031, USA
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Andrea Alù
- Photonics Initiative, Advanced Science Research Center, City University of New York, New York, NY, 10031, USA
- Department of Electrical Engineering, City College of the City University of New York, New York, NY, 10031, USA
- Physics Program, Graduate Center, City University of New York, New York, NY, 10016, USA
| | - Gabriele Grosso
- Photonics Initiative, Advanced Science Research Center, City University of New York, New York, NY, 10031, USA.
- Physics Program, Graduate Center, City University of New York, New York, NY, 10016, USA.
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5
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Li S, Ai R, Chui KK, Fang Y, Lai Y, Zhuo X, Shao L, Wang J, Lin HQ. Routing the Exciton Emissions of WS 2 Monolayer with the High-Order Plasmon Modes of Ag Nanorods. NANO LETTERS 2023; 23:4183-4190. [PMID: 37158482 PMCID: PMC10214448 DOI: 10.1021/acs.nanolett.3c00054] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Revised: 05/02/2023] [Indexed: 05/10/2023]
Abstract
Locally routing the exciton emissions in two-dimensional (2D) transition-metal dichalcogenides along different directions at the nanophotonic interface is of great interest in exploiting the promising 2D excitonic systems for functional nano-optical components. However, such control has remained elusive. Herein we report on a facile plasmonic approach for electrically controlled spatial modulation of the exciton emissions in a WS2 monolayer. The emission routing is enabled by the resonance coupling between the WS2 excitons and the multipole plasmon modes in individual silver nanorods placed on a WS2 monolayer. Different from prior demonstrations, the routing effect can be modulated by the doping level of the WS2 monolayer, enabling electrical control. Our work takes advantage of the high-quality plasmon modes supported by simple rod-shaped metal nanocrystals for the angularly resolved manipulation of 2D exciton emissions. Active control is achieved, which offers great opportunities for the development of nanoscale light sources and nanophotonic devices.
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Affiliation(s)
- Shasha Li
- Beijing
Computational Science Research Center, Beijing 100193, People’s Republic of China
- Department
of Physics, The Chinese University of Hong
Kong, Shatin, Hong Kong SAR 999077, People’s Republic of China
| | - Ruoqi Ai
- Department
of Physics, The Chinese University of Hong
Kong, Shatin, Hong Kong SAR 999077, People’s Republic of China
| | - Ka Kit Chui
- Department
of Physics, The Chinese University of Hong
Kong, Shatin, Hong Kong SAR 999077, People’s Republic of China
| | - Yini Fang
- Department
of Physics, The Chinese University of Hong
Kong, Shatin, Hong Kong SAR 999077, People’s Republic of China
| | - Yunhe Lai
- Department
of Physics, The Chinese University of Hong
Kong, Shatin, Hong Kong SAR 999077, People’s Republic of China
| | - Xiaolu Zhuo
- School
of Science and Engineering, The Chinese
University of Hong Kong (Shenzhen), Shenzhen 518172, People’s Republic of China
| | - Lei Shao
- State
Key Laboratory of Optoelectronic Materials and Technologies, Guangdong
Province Key Laboratory of Display Material and Technology, School
of Electronics and Information Technology, Sun Yat-sen University, Guangzhou 510275, People’s
Republic of China
| | - Jianfang Wang
- Department
of Physics, The Chinese University of Hong
Kong, Shatin, Hong Kong SAR 999077, People’s Republic of China
| | - Hai-Qing Lin
- Beijing
Computational Science Research Center, Beijing 100193, People’s Republic of China
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6
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Woźniak T, Faria Junior PE, Ramzan MS, Kuc AB. Electronic and Excitonic Properties of MSi 2 Z 4 Monolayers. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023; 19:e2206444. [PMID: 36772899 DOI: 10.1002/smll.202206444] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Revised: 01/20/2023] [Indexed: 05/11/2023]
Abstract
MA2 Z4 monolayers form a new class of hexagonal non-centrosymmetric materials hosting extraordinary spin-valley physics. While only two compounds (MoSi2 N4 and WSi2 N4 ) are recently synthesized, theory predicts interesting (opto)electronic properties of a whole new family of such two-dimensional (2D) materials. Here, the chemical trends of band gaps and spin-orbit splittings of bands in selected MSi2 Z4 (M = Mo, W; Z = N, P, As, Sb) compounds are studied from first-principles. Effective Bethe-Salpeter-equation-based calculations reveal high exciton binding energies. Evolution of excitonic energies under external magnetic field is predicted by providing their effective g-factors and diamagnetic coefficients, which can be directly compared to experimental values. In particular, large positive g-factors are predicted for excitons involving higher conduction bands. In view of these predictions, MSi2 Z4 monolayers yield a new platform to study excitons and are attractive for optoelectronic devices, also in the form of heterostructures. In addition, a spin-orbit induced bands inversion is observed in the heaviest studied compound, WSi2 Sb4 , a hallmark of its topological nature.
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Affiliation(s)
- Tomasz Woźniak
- Department of Semiconductor Materials Engineering, Wrocław University of Science and Technology, Wrocław, 50-370, Poland
- Department of Physics and Earth Sciences, Jacobs University Bremen, Campus Ring 1, 28759, Bremen, Germany
- Helmholtz-Zentrum Dresden-Rossendorf, Abteilung Ressourcenökologie, Forschungsstelle Leipzig, Permoserstr. 15, 04318, Leipzig, Germany
| | - Paulo E Faria Junior
- Institute for Theoretical Physics, University of Regensburg, Universitätsstraße 31, 93040, Regensburg, Germany
| | - Muhammad S Ramzan
- Department of Physics and Earth Sciences, Jacobs University Bremen, Campus Ring 1, 28759, Bremen, Germany
- Helmholtz-Zentrum Dresden-Rossendorf, Abteilung Ressourcenökologie, Forschungsstelle Leipzig, Permoserstr. 15, 04318, Leipzig, Germany
- Institut für Physik, Carl von Ossietzky Universität Oldenburg, 26129, Oldenburg, Germany
| | - Agnieszka B Kuc
- Department of Physics and Earth Sciences, Jacobs University Bremen, Campus Ring 1, 28759, Bremen, Germany
- Helmholtz-Zentrum Dresden-Rossendorf, Abteilung Ressourcenökologie, Forschungsstelle Leipzig, Permoserstr. 15, 04318, Leipzig, Germany
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7
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Faria Junior PE, Fabian J. Signatures of Electric Field and Layer Separation Effects on the Spin-Valley Physics of MoSe 2/WSe 2 Heterobilayers: From Energy Bands to Dipolar Excitons. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:1187. [PMID: 37049281 PMCID: PMC10096971 DOI: 10.3390/nano13071187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 03/22/2023] [Accepted: 03/24/2023] [Indexed: 06/19/2023]
Abstract
Multilayered van der Waals heterostructures based on transition metal dichalcogenides are suitable platforms on which to study interlayer (dipolar) excitons, in which electrons and holes are localized in different layers. Interestingly, these excitonic complexes exhibit pronounced valley Zeeman signatures, but how their spin-valley physics can be further altered due to external parameters-such as electric field and interlayer separation-remains largely unexplored. Here, we perform a systematic analysis of the spin-valley physics in MoSe2/WSe2 heterobilayers under the influence of an external electric field and changes of the interlayer separation. In particular, we analyze the spin (Sz) and orbital (Lz) degrees of freedom, and the symmetry properties of the relevant band edges (at K, Q, and Γ points) of high-symmetry stackings at 0° (R-type) and 60° (H-type) angles-the important building blocks present in moiré or atomically reconstructed structures. We reveal distinct hybridization signatures on the spin and the orbital degrees of freedom of low-energy bands, due to the wave function mixing between the layers, which are stacking-dependent, and can be further modified by electric field and interlayer distance variation. We find that H-type stackings favor large changes in the g-factors as a function of the electric field, e.g., from -5 to 3 in the valence bands of the Hhh stacking, because of the opposite orientation of Sz and Lz of the individual monolayers. For the low-energy dipolar excitons (direct and indirect in k-space), we quantify the electric dipole moments and polarizabilities, reflecting the layer delocalization of the constituent bands. Furthermore, our results show that direct dipolar excitons carry a robust valley Zeeman effect nearly independent of the electric field, but tunable by the interlayer distance, which can be rendered experimentally accessible via applied external pressure. For the momentum-indirect dipolar excitons, our symmetry analysis indicates that phonon-mediated optical processes can easily take place. In particular, for the indirect excitons with conduction bands at the Q point for H-type stackings, we find marked variations of the valley Zeeman (∼4) as a function of the electric field, which notably stands out from the other dipolar exciton species. Our analysis suggests that stronger signatures of the coupled spin-valley physics are favored in H-type stackings, which can be experimentally investigated in samples with twist angle close to 60°. In summary, our study provides fundamental microscopic insights into the spin-valley physics of van der Waals heterostructures, which are relevant to understanding the valley Zeeman splitting of dipolar excitonic complexes, and also intralayer excitons.
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Affiliation(s)
- Paulo E. Faria Junior
- Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
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8
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Zhumagulov YV, Vagov A, Gulevich DR, Perebeinos V. Electrostatic and Environmental Control of the Trion Fine Structure in Transition Metal Dichalcogenide Monolayers. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:3728. [PMID: 36364505 PMCID: PMC9656490 DOI: 10.3390/nano12213728] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Revised: 10/18/2022] [Accepted: 10/19/2022] [Indexed: 06/16/2023]
Abstract
Charged excitons or trions are essential for optical spectra in low-dimensional doped monolayers (ML) of transitional metal dichalcogenides (TMDC). Using a direct diagonalization of the three-body Hamiltonian, we calculate the low-lying trion states in four types of TMDC MLs as a function of doping and dielectric environment. We show that the fine structure of the trion is the result of the interplay between the spin-valley fine structure of the single-particle bands and the exchange interaction. We demonstrate that by variations of the doping and dielectric environment, the fine structure of the trion energy can be tuned, leading to anticrossing of the bright and dark states, with substantial implications for the optical spectra of the TMDC ML.
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Affiliation(s)
| | - Alexei Vagov
- Faculty of Physics, National Research University Higher School of Economics, 101000 Moscow, Russia
| | | | - Vasili Perebeinos
- Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, NY 14260, USA
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9
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Tiede DO, Saigal N, Ostovar H, Döring V, Lambers H, Wurstbauer U. Exciton Manifolds in Highly Ambipolar Doped WS 2. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:3255. [PMID: 36145043 PMCID: PMC9504948 DOI: 10.3390/nano12183255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Revised: 09/09/2022] [Accepted: 09/13/2022] [Indexed: 06/16/2023]
Abstract
The disentanglement of single and many particle properties in 2D semiconductors and their dependencies on high carrier concentration is challenging to experimentally study by pure optical means. We establish an electrolyte gated WS2 monolayer field-effect structure capable of shifting the Fermi level from the valence into the conduction band that is suitable to optically trace exciton binding as well as the single-particle band gap energies in the weakly doped regime. Combined spectroscopic imaging ellipsometry and photoluminescence spectroscopies spanning large n- and p-type doping with charge carrier densities up to 1014 cm-2 enable to study screening phenomena and doping dependent evolution of the rich exciton manifold whose origin is controversially discussed in literature. We show that the two most prominent emission bands in photoluminescence experiments are due to the recombination of spin-forbidden and momentum-forbidden charge neutral excitons activated by phonons. The observed interband transitions are redshifted and drastically weakened under electron or hole doping. This field-effect platform is not only suitable for studying exciton manifold but is also suitable for combined optical and transport measurements on degenerately doped atomically thin quantum materials at cryogenic temperatures.
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Affiliation(s)
- David Otto Tiede
- Institute of Physics, University of Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
- Center for Soft Nanoscience (SoN), University of Münster, Busso-Peus-Straße 10, 48149 Münster, Germany
| | - Nihit Saigal
- Institute of Physics, University of Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
- Center for Soft Nanoscience (SoN), University of Münster, Busso-Peus-Straße 10, 48149 Münster, Germany
| | - Hossein Ostovar
- Institute of Physics, University of Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
- Center for Soft Nanoscience (SoN), University of Münster, Busso-Peus-Straße 10, 48149 Münster, Germany
| | - Vera Döring
- Institute of Physics, University of Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
- Center for Soft Nanoscience (SoN), University of Münster, Busso-Peus-Straße 10, 48149 Münster, Germany
| | - Hendrik Lambers
- Institute of Physics, University of Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
- Center for Soft Nanoscience (SoN), University of Münster, Busso-Peus-Straße 10, 48149 Münster, Germany
| | - Ursula Wurstbauer
- Institute of Physics, University of Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
- Center for Soft Nanoscience (SoN), University of Münster, Busso-Peus-Straße 10, 48149 Münster, Germany
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10
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Blundo E, Junior PEF, Surrente A, Pettinari G, Prosnikov MA, Olkowska-Pucko K, Zollner K, Woźniak T, Chaves A, Kazimierczuk T, Felici M, Babiński A, Molas MR, Christianen PCM, Fabian J, Polimeni A. Strain-Induced Exciton Hybridization in WS_{2} Monolayers Unveiled by Zeeman-Splitting Measurements. PHYSICAL REVIEW LETTERS 2022; 129:067402. [PMID: 36018658 DOI: 10.1103/physrevlett.129.067402] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Accepted: 06/09/2022] [Indexed: 06/15/2023]
Abstract
Mechanical deformations and ensuing strain are routinely exploited to tune the band gap energy and to enhance the functionalities of two-dimensional crystals. In this Letter, we show that strain leads also to a strong modification of the exciton magnetic moment in WS_{2} monolayers. Zeeman-splitting measurements under magnetic fields up to 28.5 T were performed on single, one-layer-thick WS_{2} microbubbles. The strain of the bubbles causes a hybridization of k-space direct and indirect excitons resulting in a sizable decrease in the modulus of the g factor of the ground-state exciton. These findings indicate that strain may have major effects on the way the valley number of excitons can be used to process binary information in two-dimensional crystals.
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Affiliation(s)
- Elena Blundo
- Physics Department, Sapienza University of Rome, 00185 Rome, Italy
| | - Paulo E Faria Junior
- Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
| | - Alessandro Surrente
- Physics Department, Sapienza University of Rome, 00185 Rome, Italy
- Department of Experimental Physics, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, 50-370 Wrocław, Poland
| | - Giorgio Pettinari
- Institute for Photonics and Nanotechnologies, National Research Council, 00156 Rome, Italy
| | - Mikhail A Prosnikov
- High Field Magnet Laboratory, HFML-EMFL, Radboud University, 6525 ED Nijmegen, The Netherlands
| | - Katarzyna Olkowska-Pucko
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - Klaus Zollner
- Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
| | - Tomasz Woźniak
- Department of Semiconductor Materials Engineering, Wrocław University of Science and Technology, 50-370 Wrocław, Poland
| | - Andrey Chaves
- Departamento de Fisica, Universidade Federal do Ceará, 60455-900 Fortaleza, Ceará, Brazil
- Department of Physics, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerpen, Belgium
| | - Tomasz Kazimierczuk
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - Marco Felici
- Physics Department, Sapienza University of Rome, 00185 Rome, Italy
| | - Adam Babiński
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - Maciej R Molas
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
| | - Peter C M Christianen
- High Field Magnet Laboratory, HFML-EMFL, Radboud University, 6525 ED Nijmegen, The Netherlands
| | - Jaroslav Fabian
- Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
| | - Antonio Polimeni
- Physics Department, Sapienza University of Rome, 00185 Rome, Italy
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11
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Das S, Gupta G, Chatterjee S, Watanabe K, Taniguchi T, Majumdar K. Highly Nonlinear Biexcitonic Photocurrent from Ultrafast Interlayer Charge Transfer. ACS NANO 2022; 16:9728-9735. [PMID: 35604012 DOI: 10.1021/acsnano.2c03397] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Strong Coulomb interactions in monolayer semiconductors allow them to host optically active large many-body states, such as the five-particle state, charged biexciton. Strong nonlinear light absorption by the charged biexciton under spectral resonance, coupled with its charged nature, makes it intriguing for nonlinear photodetection─an area that is hitherto unexplored. Using the high built-in vertical electric field in an asymmetrically designed few-layer graphene encapsulated 1L-WS2 heterostructure, here we report a large, highly nonlinear photocurrent arising from the strong absorption by two charged biexciton species under zero external bias (self-powered mode). Time-resolved measurement reveals that the generated charged biexcitons transfer to the few-layer graphene in a time scale of sub-5 ps, indicating an ultrafast intrinsic limit of the photoresponse. By using single- and two-color photoluminescence excitation spectroscopy, we show that the two biexcitonic peaks originate from bright-dark and bright-bright exciton-trion combinations. Such innate nonlinearity in the photocurrent due to its biexcitonic origin, coupled with the ultrafast response due to swift interlayer charge transfer, exemplifies the promise of manipulating many-body effects in monolayers toward viable optoelectronic applications.
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Affiliation(s)
- Sarthak Das
- Department of Electrical Communication Engineering, Indian Institute of Science, Bangalore 560012, India
| | - Garima Gupta
- Department of Electrical Communication Engineering, Indian Institute of Science, Bangalore 560012, India
| | - Suman Chatterjee
- Department of Electrical Communication Engineering, Indian Institute of Science, Bangalore 560012, India
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-044 Japan
| | - Kausik Majumdar
- Department of Electrical Communication Engineering, Indian Institute of Science, Bangalore 560012, India
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12
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Covre FS, Faria PE, Gordo VO, de Brito CS, Zhumagulov YV, Teodoro MD, Couto ODD, Misoguti L, Pratavieira S, Andrade MB, Christianen PCM, Fabian J, Withers F, Galvão Gobato Y. Revealing the impact of strain in the optical properties of bubbles in monolayer MoSe 2. NANOSCALE 2022; 14:5758-5768. [PMID: 35348558 DOI: 10.1039/d2nr00315e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Strain plays an important role for the optical properties of monolayer transition metal dichalcogenides (TMDCs). Here, we investigate strain effects in a monolayer MoSe2 sample with a large bubble region using μ-Raman, second harmonic generation (SHG), μ-photoluminescence and magneto μ-photoluminescence at low temperature. Remarkably, our results reveal the presence of a non-uniform strain field and the observation of emission peaks at lower energies which are the signatures of exciton and trion quasiparticles red-shifted by strain effects in the bubble region, in agreement with our theoretical predictions. Furthermore, we have observed that the emission in the strained region decreases the trion binding energy and enhances the valley g-factors as compared to non-strained regions. Considering uniform biaxial strain effects within the unit cell of the TMDC monolayer (ML), our first principles calculations predict the observed enhancement of the exciton valley Zeeman effect. In addition, our results suggest that the exciton-trion fine structure plays an important role for the optical properties of strained TMDC ML. In summary, our study provides fundamental insights on the behaviour of excitons and trions in strained monolayer MoSe2 which are particularly relevant to properly characterize and understand the fine structure of excitonic complexes in strained TMDC systems/devices.
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Affiliation(s)
- F S Covre
- Departamento de Física, Universidade Federal de São Carlos, 13565-905, São Carlos, SP, Brazil.
| | - P E Faria
- Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
| | - V O Gordo
- Instituto de Física "Gleb Wataghin", Universidade Estadual de Campinas, 13083-859, Campinas, São Paulo, Brazil
| | - C Serati de Brito
- Departamento de Física, Universidade Federal de São Carlos, 13565-905, São Carlos, SP, Brazil.
| | - Y V Zhumagulov
- Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
| | - M D Teodoro
- Departamento de Física, Universidade Federal de São Carlos, 13565-905, São Carlos, SP, Brazil.
| | - O D D Couto
- Instituto de Física "Gleb Wataghin", Universidade Estadual de Campinas, 13083-859, Campinas, São Paulo, Brazil
| | - L Misoguti
- Instituto de Física de São Carlos - Universidade de São Paulo, CEP 13566-590, São Carlos, São Paulo, Brazil
| | - S Pratavieira
- Instituto de Física de São Carlos - Universidade de São Paulo, CEP 13566-590, São Carlos, São Paulo, Brazil
| | - M B Andrade
- Instituto de Física de São Carlos - Universidade de São Paulo, CEP 13566-590, São Carlos, São Paulo, Brazil
| | - P C M Christianen
- High Field Magnet Laboratory (HFML - EMFL), Radboud University, 6525 ED Nijmegen, The Netherlands
| | - J Fabian
- Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
| | - F Withers
- College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF, UK
| | - Y Galvão Gobato
- Departamento de Física, Universidade Federal de São Carlos, 13565-905, São Carlos, SP, Brazil.
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13
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Chand SB, Woods JM, Mejia E, Taniguchi T, Watanabe K, Grosso G. Visualization of Dark Excitons in Semiconductor Monolayers for High-Sensitivity Strain Sensing. NANO LETTERS 2022; 22:3087-3094. [PMID: 35290068 DOI: 10.1021/acs.nanolett.2c00436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Transition-metal dichalcogenides (TMDs) are layered materials that have a semiconducting phase with many advantageous optoelectronic properties, including tightly bound excitons and spin-valley locking. In tungsten-based TMDs, spin- and momentum-forbidden transitions give rise to dark excitons that typically are optically inaccessible but represent the lowest excitonic states of the system. Dark excitons can deeply affect the transport, dynamics, and coherence of bright excitons, hampering device performance. Therefore, it is crucial to create conditions in which these excitonic states can be visualized and controlled. Here, we show that compressive strain in WS2 enables phonon scattering of photoexcited electrons between momentum valleys, enhancing the formation of dark intervalley excitons. We show that the emission and spectral properties of momentum-forbidden excitons are accessible and strongly depend on the local strain environment that modifies the band alignment. This mechanism is further exploited for strain sensing in two-dimensional semiconductors, revealing a gauge factor exceeding 104.
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Affiliation(s)
- Saroj B Chand
- Photonics Initiative, Advanced Science Research Center, City University of New York, New York 10031, New York, United States
| | - John M Woods
- Photonics Initiative, Advanced Science Research Center, City University of New York, New York 10031, New York, United States
| | - Enrique Mejia
- Photonics Initiative, Advanced Science Research Center, City University of New York, New York 10031, New York, United States
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Gabriele Grosso
- Photonics Initiative, Advanced Science Research Center, City University of New York, New York 10031, New York, United States
- Physics Program, Graduate Center, City University of New York, New York 10016, New York, United States
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