1
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Nam K, Im J, Han GH, Park JY, Kim H, Park S, Yoo S, Haddadnezhad M, Ahn JS, Park KD, Choi S. Photoluminescence of MoS 2 on Plasmonic Gold Nanoparticles Depending on the Aggregate Size. ACS OMEGA 2024; 9:21587-21594. [PMID: 38764616 PMCID: PMC11097376 DOI: 10.1021/acsomega.4c02442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/13/2024] [Revised: 04/04/2024] [Accepted: 04/22/2024] [Indexed: 05/21/2024]
Abstract
Transition metal dichalcogenides (TMDs) are promising candidates for ultrathin functional semiconductor devices. In particular, incorporating plasmonic nanoparticles into TMD-based devices enhances the light-matter interaction for increased absorption efficiency and enables control of device performance such as electronic, electrical, and optical properties. In this heterohybrid structure, manipulating the number of TMD layers and the aggregate size of plasmonic nanoparticles is a straightforward approach to tailoring device performance. In this study, we use photoluminescence (PL) spectroscopy, which is a commonly employed technique for monitoring device performance, to analyze the changes in electronic and optical properties depending on the number of MoS2 layers and the size of the gold nanoparticle (AuNP) aggregate under nonresonant and resonant excitation conditions. The PL intensity in monolayer MoS2/AuNPs increases as the size of aggregates increases irrespective of the excitation conditions. The strain induced by AuNPs causes a red shift, but as the aggregates grow larger, the effect of p-doping increases and the blue shift becomes prominent. In multilayer MoS2/AuNPs, quenched PL intensity is observed under nonresonant excitation, while enhancement is noted under resonant excitation, which is mainly contributed by p-doping and LSPR, respectively. Remarkably, the alteration in the spectral shape due to resonant excitation is evident solely in small aggregates of AuNPs across all layers.
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Affiliation(s)
- Kiin Nam
- Department
of Physics, Incheon National University, Incheon 22012, Republic of Korea
| | - Jaeseung Im
- Department
of Physics, Incheon National University, Incheon 22012, Republic of Korea
| | - Gang Hee Han
- Department
of Physics, Incheon National University, Incheon 22012, Republic of Korea
| | - Jin Young Park
- Department
of Physics, Incheon National University, Incheon 22012, Republic of Korea
| | - Hyuntae Kim
- System
Research & Development System Integration Team, Park Systems Corporation, Suwon 16229, Republic
of Korea
| | - Sungho Park
- Department
of Chemistry, Yonsei University, Seoul 03722, Republic of Korea
| | - Sungjae Yoo
- Biomaterials
Research Center, Biomedical Research Division, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea
| | | | - Jae Sung Ahn
- Medical &
Bio Photonics Research Center, Korea Photonics
Technology Institute, Gwangju 61007, Republic
of Korea
| | - Kyoung-Duck Park
- Department
of Physics, Pohang University of Science
and Technology, Pohang 37673, Republic of Korea
| | - Soobong Choi
- Department
of Physics, Incheon National University, Incheon 22012, Republic of Korea
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2
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Zhang R, Gan L, Zhang D, Sun H, Li Y, Ning CZ. Extreme Thermal Insulation and Tradeoff of Thermal Transport Mechanisms between Graphene and WS 2 Monolayers. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2313753. [PMID: 38403869 DOI: 10.1002/adma.202313753] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2023] [Revised: 02/21/2024] [Indexed: 02/27/2024]
Abstract
Controlling and understanding the heat flow at a nanometer scale are challenging, but important for fundamental science and applications. Two-dimensional (2D) layered materials provide perhaps the ultimate solution for meeting these challenges. While there have been reports of low thermal conductivities (several mW m-1 K-1) across the 2D heterostructures, phonon-dominant thermal transport remains strong due to the nearly-ideal contact between the layers. Here, this work experimentally explores the heat transport mechanisms by increasing the interlayer distance from perfect contact to a few nanometers and demonstrates that the phonon-dominated thermal conductivity across the WS2/graphene interface decreases further with the increasing interlayer distance until the air-dominated thermal conductivity increases again. This work finds that the resulting tradeoff of the two heat conduction mechanisms leads to the existence of a minimum thermal conductivity at 2.11 nm of 1.41 × 10-5 W m-1 K-1, which is two thousandths of the smallest value reported previously. This work provides an effective methodology for engineering thermal insulation structures and understanding heat transport at the ultimate small scales.
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Affiliation(s)
- Ruiling Zhang
- Department of Electronic Engineering, Tsinghua University, Beijing, 100084, China
- College of Integrated Circuits and Optoelectronic Chips, Shenzhen Technology University, Shenzhen, 518118, China
| | - Lin Gan
- Department of Electronic Engineering, Tsinghua University, Beijing, 100084, China
| | - Danyang Zhang
- Department of Electronic Engineering, Tsinghua University, Beijing, 100084, China
- College of Integrated Circuits and Optoelectronic Chips, Shenzhen Technology University, Shenzhen, 518118, China
| | - Hao Sun
- Department of Electronic Engineering, Tsinghua University, Beijing, 100084, China
| | - Yongzhuo Li
- Department of Electronic Engineering, Tsinghua University, Beijing, 100084, China
| | - Cun-Zheng Ning
- Department of Electronic Engineering, Tsinghua University, Beijing, 100084, China
- College of Integrated Circuits and Optoelectronic Chips, Shenzhen Technology University, Shenzhen, 518118, China
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3
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Dong S, Beaulieu S, Selig M, Rosenzweig P, Christiansen D, Pincelli T, Dendzik M, Ziegler JD, Maklar J, Xian RP, Neef A, Mohammed A, Schulz A, Stadler M, Jetter M, Michler P, Taniguchi T, Watanabe K, Takagi H, Starke U, Chernikov A, Wolf M, Nakamura H, Knorr A, Rettig L, Ernstorfer R. Observation of ultrafast interfacial Meitner-Auger energy transfer in a Van der Waals heterostructure. Nat Commun 2023; 14:5057. [PMID: 37598179 PMCID: PMC10439896 DOI: 10.1038/s41467-023-40815-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2023] [Accepted: 08/11/2023] [Indexed: 08/21/2023] Open
Abstract
Atomically thin layered van der Waals heterostructures feature exotic and emergent optoelectronic properties. With growing interest in these novel quantum materials, the microscopic understanding of fundamental interfacial coupling mechanisms is of capital importance. Here, using multidimensional photoemission spectroscopy, we provide a layer- and momentum-resolved view on ultrafast interlayer electron and energy transfer in a monolayer-WSe2/graphene heterostructure. Depending on the nature of the optically prepared state, we find the different dominating transfer mechanisms: while electron injection from graphene to WSe2 is observed after photoexcitation of quasi-free hot carriers in the graphene layer, we establish an interfacial Meitner-Auger energy transfer process following the excitation of excitons in WSe2. By analysing the time-energy-momentum distributions of excited-state carriers with a rate-equation model, we distinguish these two types of interfacial dynamics and identify the ultrafast conversion of excitons in WSe2 to valence band transitions in graphene. Microscopic calculations find interfacial dipole-monopole coupling underlying the Meitner-Auger energy transfer to dominate over conventional Förster- and Dexter-type interactions, in agreement with the experimental observations. The energy transfer mechanism revealed here might enable new hot-carrier-based device concepts with van der Waals heterostructures.
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Affiliation(s)
- Shuo Dong
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany.
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.
| | - Samuel Beaulieu
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany
- Université de Bordeaux - CNRS - CEA, CELIA, UMR5107, F33405, Talence, France
| | - Malte Selig
- Nichtlineare Optik und Quantenelektronik, Institut für Theoretische Physik, Technische Universität Berlin, 10623, Berlin, Germany
| | - Philipp Rosenzweig
- Max Planck Institute for Solid State Research, 70569, Stuttgart, Germany
| | - Dominik Christiansen
- Nichtlineare Optik und Quantenelektronik, Institut für Theoretische Physik, Technische Universität Berlin, 10623, Berlin, Germany
| | - Tommaso Pincelli
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany
| | - Maciej Dendzik
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany
- Department of Applied Physics, KTH Royal Institute of Technology, Hannes Alfvéns väg 12, 114 19, Stockholm, Sweden
| | - Jonas D Ziegler
- Institute of Applied Physics and Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062, Dresden, Germany
- Photonics Laboratory, ETH Zürich, 8093, Zürich, Switzerland
| | - Julian Maklar
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany
| | - R Patrick Xian
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany
- Department of Statistical Sciences, University of Toronto, 700 University Avenue, Toronto, ON, M5G 1Z5, Canada
| | - Alexander Neef
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany
| | - Avaise Mohammed
- Max Planck Institute for Solid State Research, 70569, Stuttgart, Germany
| | - Armin Schulz
- Max Planck Institute for Solid State Research, 70569, Stuttgart, Germany
| | - Mona Stadler
- Institute of Semiconductor Optics and Functional Interfaces, Research Center SCoPE and IQST, University of Stuttgart, 70569, Stuttgart, Germany
| | - Michael Jetter
- Institute of Semiconductor Optics and Functional Interfaces, Research Center SCoPE and IQST, University of Stuttgart, 70569, Stuttgart, Germany
| | - Peter Michler
- Institute of Semiconductor Optics and Functional Interfaces, Research Center SCoPE and IQST, University of Stuttgart, 70569, Stuttgart, Germany
| | - Takashi Taniguchi
- International 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
| | - Hidenori Takagi
- Max Planck Institute for Solid State Research, 70569, Stuttgart, Germany
- Department of Physics, University of Tokyo, 113-0033, Tokyo, Japan
- Institute for Functional Matter and Quantum Technologies, University of Stuttgart, 70569, Stuttgart, Germany
| | - Ulrich Starke
- Max Planck Institute for Solid State Research, 70569, Stuttgart, Germany
| | - Alexey Chernikov
- Institute of Applied Physics and Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062, Dresden, Germany
| | - Martin Wolf
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany
| | - Hiro Nakamura
- Max Planck Institute for Solid State Research, 70569, Stuttgart, Germany
- Department of Physics, University of Arkansas, Fayetteville, AR, 72701, USA
| | - Andreas Knorr
- Nichtlineare Optik und Quantenelektronik, Institut für Theoretische Physik, Technische Universität Berlin, 10623, Berlin, Germany
| | - Laurenz Rettig
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany.
| | - Ralph Ernstorfer
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany.
- Institut für Optik und Atomare Physik, Technische Universität Berlin, 10623, Berlin, Germany.
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4
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Biswas S, Champagne A, Haber JB, Pokawanvit S, Wong J, Akbari H, Krylyuk S, Watanabe K, Taniguchi T, Davydov AV, Al Balushi ZY, Qiu DY, da Jornada FH, Neaton JB, Atwater HA. Rydberg Excitons and Trions in Monolayer MoTe 2. ACS NANO 2023; 17:7685-7694. [PMID: 37043483 DOI: 10.1021/acsnano.3c00145] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Monolayer transition metal dichalcogenide (TMDC) semiconductors exhibit strong excitonic optical resonances, which serve as a microscopic, noninvasive probe into their fundamental properties. Like the hydrogen atom, such excitons can exhibit an entire Rydberg series of resonances. Excitons have been extensively studied in most TMDCs (MoS2, MoSe2, WS2, and WSe2), but detailed exploration of excitonic phenomena has been lacking in the important TMDC material molybdenum ditelluride (MoTe2). Here, we report an experimental investigation of excitonic luminescence properties of monolayer MoTe2 to understand the excitonic Rydberg series, up to 3s. We report a significant modification of emission energies with temperature (4 to 300 K), thereby quantifying the exciton-phonon coupling. Furthermore, we observe a strongly gate-tunable exciton-trion interplay for all the Rydberg states governed mainly by free-carrier screening, Pauli blocking, and band gap renormalization in agreement with the results of first-principles GW plus Bethe-Salpeter equation approach calculations. Our results help bring monolayer MoTe2 closer to its potential applications in near-infrared optoelectronics and photonic devices.
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Affiliation(s)
- Souvik Biswas
- Thomas J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, California 91125, United States
- Kavli Nanoscience Institute, Pasadena, California 91125, United States
| | - Aurélie Champagne
- Materials and Chemical Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Department of Physics, University of California Berkeley, Berkeley, California 94720, United States
| | - Jonah B Haber
- Department of Physics, University of California Berkeley, Berkeley, California 94720, United States
| | - Supavit Pokawanvit
- Department of Applied Physics, Stanford University, Stanford, California 94305, United States
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
| | - Joeson Wong
- Thomas J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, California 91125, United States
- Kavli Nanoscience Institute, Pasadena, California 91125, United States
| | - Hamidreza Akbari
- Thomas J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, California 91125, United States
| | - Sergiy Krylyuk
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - 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
| | - Albert V Davydov
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Zakaria Y Al Balushi
- Thomas J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, California 91125, United States
| | - Diana Y Qiu
- Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520, United States
| | - Felipe H da Jornada
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
| | - Jeffrey B Neaton
- Materials and Chemical Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Department of Physics, University of California Berkeley, Berkeley, California 94720, United States
- Kavli Energy Nanosciences Institute at Berkeley, Berkeley, California 94720, United States
| | - Harry A Atwater
- Thomas J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, California 91125, United States
- Kavli Nanoscience Institute, Pasadena, California 91125, United States
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5
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Shu H. Two Janus Ga 2STe monolayers and their electronic, optical, and photocatalytic properties. Phys Chem Chem Phys 2023; 25:7937-7945. [PMID: 36862092 DOI: 10.1039/d3cp00070b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
Abstract
Recently, two-dimensional Janus materials have attracted increasing interest due to their unique structure and novel properties. Based on density-functional and many-body perturbation theories (i.e. DFT + G0W0 + BSE methods), the electronic, optical, and photocatalytic properties of Janus Ga2STe monolayers with two configurations are explored systematically. It is found that the two Janus Ga2STe monolayers exhibit high dynamical and thermal stabilities and have desirable direct gaps of about 2 eV at the G0W0 level. Their optical absorption spectra are dominated by the enhanced excitonic effects, in which bright bound excitons possess moderate binding energies of about 0.6 eV. Most interestingly, Janus Ga2STe monolayers show high light absorption coefficients (larger than 106 cm-1) in the visible light region, effective spatial separation of photoexcited carriers, and suitable band edge positions, which make them potential candidates for photoelectronic and photocatalytic devices. These observed findings enrich the deep understanding of the properties of Janus Ga2STe monolayers.
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Affiliation(s)
- Huabing Shu
- School of Science, Jiangsu University of Science and Technology, Zhenjiang 212001, China.
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6
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Liu F. Time- and angle-resolved photoemission spectroscopy (TR-ARPES) of TMDC monolayers and bilayers. Chem Sci 2023; 14:736-750. [PMID: 36755720 PMCID: PMC9890651 DOI: 10.1039/d2sc04124c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Accepted: 12/04/2022] [Indexed: 12/12/2022] Open
Abstract
Many unique properties in two-dimensional (2D) materials and their heterostructures rely on charge excitation, scattering, transfer, and relaxation dynamics across different points in the momentum space. Understanding these dynamics is crucial in both the fundamental study of 2D physics and their incorporation in optoelectronic and quantum devices. A direct method to probe charge carrier dynamics with momentum resolution is time- and angle-resolved photoemission spectroscopy (TR-ARPES). Such measurements have been challenging, since photoexcited carriers in many 2D monolayers reside at high crystal momenta, requiring probe photon energies in the extreme UV (EUV) regime. These challenges have been recently addressed by development of table-top pulsed EUV sources based on high harmonic generation, and the successful integration into a TR-ARPES and/or time-resolved momentum microscope. Such experiments will allow direct imaging of photoelectrons with superior time, energy, and crystal momentum resolution, with unique advantage over traditional optical measurements. Recently, TR-ARPES experiments of 2D transition metal dichalcogenide (TMDC) monolayers and bilayers have created unprecedented opportunities to reveal many intrinsic dynamics of 2D materials, such as bandgap renormalization, charge carrier scattering, relaxation, and wavefunction localization in moiré patterns. This perspective aims to give a short review of recent discoveries and discuss the challenges and opportunities of such techniques in the future.
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Affiliation(s)
- Fang Liu
- Department of Chemistry and the PULSE Institute, Stanford University Stanford California 94305 USA
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7
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Nanocavity-induced trion emission from atomically thin WSe 2. Sci Rep 2022; 12:15861. [PMID: 36151265 PMCID: PMC9508186 DOI: 10.1038/s41598-022-20226-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Accepted: 09/09/2022] [Indexed: 11/08/2022] Open
Abstract
Exciton is a bosonic quasiparticle consisting of a pair of electron and hole, with promising potentials for optoelectronic device applications, such as exciton transistors, photodetectors and light emitting devices. However, the charge-neutral nature of excitons renders them challenging to manipulate using electronics. Here we present the generation of trions, a form of charged excitons, together with enhanced exciton resonance in monolayer WSe2. The excitation of the trion quasiparticles is achieved by the hot carrier transport from the integrated gold plasmonic nanocavity, formed by embedding monolayer WSe2 between gold nanoparticles and a gold film. The nanocavity-induced negatively charged trions provide a promising route for the manipulation of excitons, essential for the construction of all-exciton information processing circuits.
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8
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Yang XC, Yu H, Yao W. Chiral Excitonics in Monolayer Semiconductors on Patterned Dielectrics. PHYSICAL REVIEW LETTERS 2022; 128:217402. [PMID: 35687445 DOI: 10.1103/physrevlett.128.217402] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2021] [Revised: 02/10/2022] [Accepted: 04/11/2022] [Indexed: 06/15/2023]
Abstract
Monolayer transition metal dichalcogenides feature tightly bound bright excitons at the degenerate valleys, where electron-hole Coulomb exchange interaction strongly couples the valley pseudospin to the momentum of the exciton. Placed on a periodically structured dielectric substrate, the spatial modulation of the Coulomb interaction leads to the formation of exciton Bloch states with real-space valley pseudospin texture displayed in a mesoscopic supercell. We find this spatial valley texture in the exciton Bloch function is pattern locked to the propagation direction, enabling nano-optical excitation of directional exciton flow through the valley selection rule. The left-right directionality of the injected exciton current is controlled by the circular polarization of excitation, while the angular directionality is controlled by the excitation location, exhibiting a vortex pattern in a supercell. The phenomenon is reminiscent of the chiral light-matter interaction in nanophotonics structures, with the role of the guided electromagnetic wave now replaced by the valley-orbit coupled exciton Bloch wave in a uniform monolayer, which points to new excitonic devices with nonreciprocal functionalities.
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Affiliation(s)
- Xu-Chen Yang
- Department of Physics, The University of Hong Kong, Hong Kong, China
- HKU-UCAS Joint Institute of Theoretical and Computational Physics at Hong Kong, China
| | - Hongyi Yu
- Guangdong Provincial Key Laboratory of Quantum Metrology and Sensing and School of Physics and Astronomy, Sun Yat-Sen University (Zhuhai Campus), Zhuhai 519082, China
| | - Wang Yao
- Department of Physics, The University of Hong Kong, Hong Kong, China
- HKU-UCAS Joint Institute of Theoretical and Computational Physics at Hong Kong, China
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9
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Rahman R, Karmakar M, Samanta D, Pathak A, Datta PK, Nath TK. One order enhancement of charge carrier relaxation rate by tuning structural and optical properties in annealed cobalt doped MoS 2 nanosheets. NEW J CHEM 2022. [DOI: 10.1039/d1nj05446e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The effective manipulation of excitons is crucial for the realization of exciton-based devices and circuits, and doping is considered a good strategy to achieve this.
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Affiliation(s)
- Rosy Rahman
- Department of Physics, Indian Institute of Technology Kharagpur, W.B., 721302, India
| | - Manobina Karmakar
- Department of Physics, Indian Institute of Technology Kharagpur, W.B., 721302, India
| | - Dipanjan Samanta
- Department of Chemistry, Indian Institute of Technology Kharagpur, W.B., 721302, India
| | - Amita Pathak
- Department of Chemistry, Indian Institute of Technology Kharagpur, W.B., 721302, India
| | - Prasanta Kumar Datta
- Department of Physics, Indian Institute of Technology Kharagpur, W.B., 721302, India
| | - Tapan Kumar Nath
- Department of Physics, Indian Institute of Technology Kharagpur, W.B., 721302, India
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10
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Biswas S, Grajower MY, Watanabe K, Taniguchi T, Atwater HA. Broadband electro-optic polarization conversion with atomically thin black phosphorus. Science 2021; 374:448-453. [PMID: 34672749 DOI: 10.1126/science.abj7053] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- Souvik Biswas
- Thomas J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, CA 91125, USA
| | - Meir Y Grajower
- Thomas J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, CA 91125, USA
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials, Nanoarchitectonics, National Institute for Materials Science, Tsukuba 305-0044, Japan
| | - Harry A Atwater
- Thomas J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, CA 91125, USA
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11
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Li M, Biswas S, Hail CU, Atwater HA. Refractive Index Modulation in Monolayer Molybdenum Diselenide. NANO LETTERS 2021; 21:7602-7608. [PMID: 34468150 DOI: 10.1021/acs.nanolett.1c02199] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Two-dimensional transition metal dichalcogenides are promising candidates for ultrathin light modulators due to their highly tunable excitonic resonances at visible and near-infrared wavelengths. At cryogenic temperatures, large excitonic reflectivity in monolayer molybdenum diselenide (MoSe2) has been shown, but the permittivity and index modulation have not been studied. Here, we demonstrate large gate-tunability of complex refractive index in monolayer MoSe2 by Fermi level modulation and study the doping dependence of the A and B excitonic resonances for temperatures between 4 and 150 K. By tuning the charge density, we observe both temperature- and carrier-dependent epsilon-near-zero response in the permittivity and transition from metallic to dielectric near the A exciton energy. We attribute the dynamic control of the refractive index to the interplay between radiative and non-radiative decay channels that are tuned upon gating. Our results suggest the potential of monolayer MoSe2 as an active material for emerging photonics applications.
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Affiliation(s)
- Melissa Li
- Thomas J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, California 91125, United States
| | - Souvik Biswas
- Thomas J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, California 91125, United States
| | - Claudio U Hail
- Thomas J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, California 91125, United States
| | - Harry A Atwater
- Thomas J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, California 91125, United States
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12
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Xu Y, Horn C, Zhu J, Tang Y, Ma L, Li L, Liu S, Watanabe K, Taniguchi T, Hone JC, Shan J, Mak KF. Creation of moiré bands in a monolayer semiconductor by spatially periodic dielectric screening. NATURE MATERIALS 2021; 20:645-649. [PMID: 33479527 DOI: 10.1038/s41563-020-00888-y] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Accepted: 11/24/2020] [Indexed: 06/12/2023]
Abstract
Moiré superlattices of two-dimensional van der Waals materials have emerged as a powerful platform for designing electronic band structures and discovering emergent physical phenomena. A key concept involves the creation of long-wavelength periodic potential and moiré bands in a crystal through interlayer electronic hybridization or atomic corrugation when two materials are overlaid. Here we demonstrate a new approach based on spatially periodic dielectric screening to create moiré bands in a monolayer semiconductor. This approach relies on reduced dielectric screening of the Coulomb interactions in monolayer semiconductors and their environmental dielectric-dependent electronic band structure. We observe optical transitions between moiré bands in monolayer WSe2 when it is placed close to small-angle-misaligned graphene on hexagonal boron nitride. The moiré bands are a result of long-range Coulomb interactions, which are strongly gate tunable, and can have versatile superlattice symmetries independent of the crystal lattice of the host material. Our result also demonstrates that monolayer semiconductors are sensitive local dielectric sensors.
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Affiliation(s)
- Yang Xu
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
| | - Connor Horn
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
| | - Jiacheng Zhu
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
| | - Yanhao Tang
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
| | - Liguo Ma
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
| | - Lizhong Li
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
| | - Song Liu
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - Kenji Watanabe
- National Institute for Materials Science, Tsukuba, Japan
| | | | - James C Hone
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - Jie Shan
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA.
- Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY, USA.
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY, USA.
| | - Kin Fai Mak
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA.
- Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY, USA.
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY, USA.
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13
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Correlated insulating states at fractional fillings of moiré superlattices. Nature 2020; 587:214-218. [PMID: 33177668 DOI: 10.1038/s41586-020-2868-6] [Citation(s) in RCA: 145] [Impact Index Per Article: 36.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Accepted: 09/03/2020] [Indexed: 11/08/2022]
Abstract
Quantum particles on a lattice with competing long-range interactions are ubiquitous in physics; transition metal oxides1,2, layered molecular crystals3 and trapped-ion arrays4 are a few examples. In the strongly interacting regime, these systems often show a rich variety of quantum many-body ground states that challenge theory2. The emergence of transition metal dichalcogenide moiré superlattices provides a highly controllable platform in which to study long-range electronic correlations5-12. Here we report an observation of nearly two dozen correlated insulating states at fractional fillings of tungsten diselenide/tungsten disulfide moiré superlattices. This finding is enabled by a new optical sensing technique that is based on the sensitivity to the dielectric environment of the exciton excited states in a single-layer semiconductor of tungsten diselenide. The cascade of insulating states shows an energy ordering that is nearly symmetric about a filling factor of half a particle per superlattice site. We propose a series of charge-ordered states at commensurate filling fractions that range from generalized Wigner crystals7 to charge density waves. Our study lays the groundwork for using moiré superlattices to simulate a wealth of quantum many-body problems that are described by the two-dimensional extended Hubbard model3,13,14 or spin models with long-range charge-charge and exchange interactions15,16.
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14
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Liu S, Granados Del Águila A, Liu X, Zhu Y, Han Y, Chaturvedi A, Gong P, Yu H, Zhang H, Yao W, Xiong Q. Room-Temperature Valley Polarization in Atomically Thin Semiconductors via Chalcogenide Alloying. ACS NANO 2020; 14:9873-9883. [PMID: 32806059 DOI: 10.1021/acsnano.0c02703] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Room-temperature manipulation and processing of information encoded in the electronic valley pseudospin and spin degrees of freedoms lie at the heart of the next technological quantum revolution. In atomically thin layers of transition-metal dichalcogenides (TMDs) with hexagonal lattices, valley-polarized excitations and valley quantum coherence can be generated by simply shining with adequately polarized light. In turn, the polarization states of light can induce topological Hall currents in the absence of an external magnetic field, which underlies the fundamental principle of opto-valleytronics devices. However, demonstration of optical generation of valley polarization at room temperature has remained challenging and not well understood. Here, we demonstrate control of strong valley polarization (valley quantum coherence) at room temperature of up to ∼50% (∼20%) by strategically designing Coulomb forces and spin-orbit interactions in atomically thin TMDs via chalcogenide alloying. We show that tailor making the carrier density and the relative order between optically active (bright) and forbidden (dark) states by key variations on the chalcogenide atom ratio allows full control of valley pseudospin dynamics. Our findings set a comprehensive approach for intrinsic and efficient manipulation of valley pseudospin and spin degree of freedom toward realistic opto-valleytronics devices.
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Affiliation(s)
- Sheng Liu
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Andrés Granados Del Águila
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Xue Liu
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Yihan Zhu
- Advance Membrane and Porous Materials Center, Division of Physical and Engineering, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia
- Center for Electron Microscopy and State Key Laboratory Breeding Base of Green Chemistry Synthesis Technology, College of Chemical Engineering, Zhejiang University of Technology, Hangzhou 310014, China
| | - Yu Han
- Advance Membrane and Porous Materials Center, Division of Physical and Engineering, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia
| | - Apoorva Chaturvedi
- School of Material Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
| | - Pu Gong
- Department of Physics and Center of Theoretical and Computational Physics, University of Hong Kong, Hong Kong, China
| | - Hongyi Yu
- Guangdong Provincial Key Laboratory of Quantum Metrology and Sensing and School of Physics and Astronomy, Sun Yat-Sen University (Zhuhai Campus), Zhuhai 519082, China
| | - Hua Zhang
- Department of Chemistry and Hong Kong Branch of National Precious Metals Material Engineering Research Centre (NPMM), City University of Hong Kong, Hong Kong, China
| | - Wang Yao
- Department of Physics and Center of Theoretical and Computational Physics, University of Hong Kong, Hong Kong, China
| | - Qihua Xiong
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
- State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, China
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15
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Cunningham PD, Hanbicki AT, Reinecke TL, McCreary KM, Jonker BT. Resonant optical Stark effect in monolayer WS 2. Nat Commun 2019; 10:5539. [PMID: 31804477 PMCID: PMC6895111 DOI: 10.1038/s41467-019-13501-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Accepted: 11/07/2019] [Indexed: 11/24/2022] Open
Abstract
Breaking the valley degeneracy in monolayer transition metal dichalcogenides through the valley-selective optical Stark effect (OSE) can be exploited for classical and quantum valleytronic operations such as coherent manipulation of valley superposition states. The strong light-matter interactions responsible for the OSE have historically been described by a two-level dressed-atom model, which assumes noninteracting particles. Here we experimentally show that this model, which works well in semiconductors far from resonance, does not apply for excitation near the exciton resonance in monolayer WS2. Instead, we show that an excitonic model of the OSE, which includes many-body Coulomb interactions, is required. We confirm the prediction from this theory that many-body effects between virtual excitons produce a dominant blue-shift for photoexcitation detuned from resonance by less than the exciton binding energy. As such, we suggest that our findings are general to low-dimensional semiconductors that support bound excitons and other many-body Coulomb interactions. Many-body interactions have important consequences for the optoelectronic properties of 2D materials. Here, the authors report on how many-body interactions affect the behavior of the valley-selective optical Stark effect for excitation near the A-exciton resonance in monolayer WS2.
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Affiliation(s)
- Paul D Cunningham
- U.S. Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC, 20375, USA.
| | - Aubrey T Hanbicki
- U.S. Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC, 20375, USA.,Laboratory for Physical Sciences, University of Maryland, 8050 Greenmead Drive, College Park, MD, 20740, USA
| | - Thomas L Reinecke
- U.S. Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC, 20375, USA
| | - Kathleen M McCreary
- U.S. Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC, 20375, USA
| | - Berend T Jonker
- U.S. Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC, 20375, USA
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16
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Pu J, Matsuki K, Chu L, Kobayashi Y, Sasaki S, Miyata Y, Eda G, Takenobu T. Exciton Polarization and Renormalization Effect for Optical Modulation in Monolayer Semiconductors. ACS NANO 2019; 13:9218-9226. [PMID: 31394038 DOI: 10.1021/acsnano.9b03563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The ideal quantum confinement structure of monolayer semiconductors offers prominent optical modulation capabilities that are mediated by enhanced many-body interactions. Herein, we establish an electrolyte-gating method for tuning the luminescence properties that are in transition metal dichalcogenide (TMDC) monolayers. We fabricate electric double-layer capacitors on TMDC/graphite heterostructures to investigate electric-field- and carrier-density-dependent photoluminescence. The exciton peak energy initially shows a slight quadratic red shift of ∼1 meV without carrier accumulations, which is caused by the quantum-confined Stark effect. In contrast, the exciton resonance exhibits a larger red shift up to 10 meV with the accumulated carrier density above 1013 cm-2. These results indicate that the optical transitions can be largely modulated by the carrier density control in S- and Se-based TMDCs, as triggered by the doping-induced band gap renormalization effect. To further inspire this modulation capability, we also apply our method to electrolyte-based TMDC light-emitting devices. Biasing solely in electrolyte-induced p-i-n junctions yields pronounced red shifts up to 40 meV for exciton and trion electroluminescence. Consequently, our approach reveals that the doping effects in the high-carrier-density regimes are potentially significant for efficient optical modulation in monolayer semiconductors.
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Affiliation(s)
- Jiang Pu
- Department of Applied Physics , Nagoya University , Nagoya 464-8603 , Japan
| | - Keichiro Matsuki
- Department of Advanced Science and Engineering , Waseda University , Tokyo 169-8555 , Japan
| | - Leiqiang Chu
- Department of Physics , National University of Singapore , 117551 Singapore
- Centre for Advanced 2D Materials , 117542 Singapore
| | - Yu Kobayashi
- Department of Physics , Tokyo Metropolitan University , Tokyo 192-0397 , Japan
| | - Shogo Sasaki
- Department of Physics , Tokyo Metropolitan University , Tokyo 192-0397 , Japan
| | - Yasumitsu Miyata
- Department of Physics , Tokyo Metropolitan University , Tokyo 192-0397 , Japan
| | - Goki Eda
- Department of Physics , National University of Singapore , 117551 Singapore
- Centre for Advanced 2D Materials , 117542 Singapore
- Department of Chemistry , National University of Singapore , 117542 Singapore
| | - Taishi Takenobu
- Department of Applied Physics , Nagoya University , Nagoya 464-8603 , Japan
- Department of Advanced Science and Engineering , Waseda University , Tokyo 169-8555 , Japan
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17
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Nguyen PV, Teutsch NC, Wilson NP, Kahn J, Xia X, Graham AJ, Kandyba V, Giampietri A, Barinov A, Constantinescu GC, Yeung N, Hine NDM, Xu X, Cobden DH, Wilson NR. Visualizing electrostatic gating effects in two-dimensional heterostructures. Nature 2019; 572:220-223. [DOI: 10.1038/s41586-019-1402-1] [Citation(s) in RCA: 84] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 05/07/2019] [Indexed: 11/09/2022]
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18
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Xu S, Yang J, Jiang H, Su F, Zeng Z. Transient photoconductivity and free carrier dynamics in a monolayer WS 2 probed by time resolved Terahertz spectroscopy. NANOTECHNOLOGY 2019; 30:265706. [PMID: 30861497 DOI: 10.1088/1361-6528/ab0f02] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The frequency and time resolved conductivity in a photoexcited large-area monolayer tungsten disulfide (WS2) have been simultaneously determined by using time-resolved terahertz spectroscopy. We use the Drude-Smith model to successfully reproduce the transient photoconductivity spectra, which demonstrate that localized free carriers, not bounded excitons, are responsible for the THz transport. Upon the optical excitation with 400 nm and 530 nm wavelength, the relaxation dynamics of the free carriers include fast and slow decay components with time constants approximately smaller than 1 ps and between 5-7 ps, respectively. The former sub-picosecond decay is attributed to the charge carrier loss induced by the exciton formation, while both the Auger recombination and the surface trapping can contribute to the slow relaxation.
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Affiliation(s)
- Shujuan Xu
- Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, People's Republic of China. University of Science and Technology of China, Hefei 230026, People's Republic of China
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19
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Liu F, Ziffer ME, Hansen KR, Wang J, Zhu X. Direct Determination of Band-Gap Renormalization in the Photoexcited Monolayer MoS_{2}. PHYSICAL REVIEW LETTERS 2019; 122:246803. [PMID: 31322407 DOI: 10.1103/physrevlett.122.246803] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Indexed: 06/10/2023]
Abstract
A key feature of monolayer semiconductors, such as transition-metal dichalcogenides, is the poorly screened Coulomb potential, which leads to a large exciton binding energy (E_{b}) and strong renormalization of the quasiparticle band gap (E_{g}) by carriers. The latter has been difficult to determine due to a cancellation in changes of E_{b} and E_{g}, resulting in little change in optical transition energy at different carrier densities. Here, we quantify band-gap renormalization in macroscopic single crystal MoS_{2} monolayers on SiO_{2} using time and angle-resolved photoemission spectroscopy. At an excitation density above the Mott threshold, E_{g} decreases by as much as 360 meV. We compare the carrier density-dependent E_{g} with previous theoretical calculations and show the necessity of knowing both doping and excitation densities in quantifying the band gap.
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Affiliation(s)
- Fang Liu
- Department of Chemistry, Columbia University, New York, New York 10027, USA
| | - Mark E Ziffer
- Department of Chemistry, Columbia University, New York, New York 10027, USA
| | - Kameron R Hansen
- Department of Chemistry, Columbia University, New York, New York 10027, USA
| | - Jue Wang
- Department of Chemistry, Columbia University, New York, New York 10027, USA
| | - Xiaoyang Zhu
- Department of Chemistry, Columbia University, New York, New York 10027, USA
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20
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Chakraborty B, Gu J, Sun Z, Khatoniar M, Bushati R, Boehmke AL, Koots R, Menon VM. Control of Strong Light-Matter Interaction in Monolayer WS 2 through Electric Field Gating. NANO LETTERS 2018; 18:6455-6460. [PMID: 30160968 DOI: 10.1021/acs.nanolett.8b02932] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Strong light-matter coupling results in the formation of half-light half-matter quasiparticles that take on the desirable properties of both systems such as small mass and large interactions. Controlling this coupling strength in real-time is highly desirable due to the large change in optical properties such as reflectivity that can be induced in strongly coupled systems. Here we demonstrate modulation of strong exciton-photon coupling in a monolayer WS2 through electric field induced gating at room temperature. The device consists of a WS2 field effect transistor embedded inside a microcavity structure which transitions from strong to weak coupling when the monolayer WS2 becomes more n-type under gating. This transition occurs due to the reduction in oscillator strength of the excitons arising from decreased Coulomb interaction in the presence of electrostatically induced free carriers. The possibility to electrically modulate a solid state system at room temperature from strong to weak coupling is highly desirable for realizing low energy optoelectronic switches and modulators operating both in quantum and classical regimes.
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Affiliation(s)
- Biswanath Chakraborty
- Department of Physics, City College of New York , City University of New York , New York 10031 , United States
| | - Jie Gu
- Department of Physics, City College of New York , City University of New York , New York 10031 , United States
- Department of Physics, The Graduate Center , City University of New York , New York 10016 , United States
| | - Zheng Sun
- Department of Physics, City College of New York , City University of New York , New York 10031 , United States
- Department of Physics, The Graduate Center , City University of New York , New York 10016 , United States
| | - Mandeep Khatoniar
- Department of Physics, City College of New York , City University of New York , New York 10031 , United States
- Department of Physics, The Graduate Center , City University of New York , New York 10016 , United States
| | - Rezlind Bushati
- Department of Physics, City College of New York , City University of New York , New York 10031 , United States
- Department of Physics, The Graduate Center , City University of New York , New York 10016 , United States
| | - Alexandra L Boehmke
- Department of Physics, City College of New York , City University of New York , New York 10031 , United States
| | - Rian Koots
- Department of Physics, City College of New York , City University of New York , New York 10031 , United States
| | - Vinod M Menon
- Department of Physics, City College of New York , City University of New York , New York 10031 , United States
- Department of Physics, The Graduate Center , City University of New York , New York 10016 , United States
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21
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Miyauchi Y, Konabe S, Wang F, Zhang W, Hwang A, Hasegawa Y, Zhou L, Mouri S, Toh M, Eda G, Matsuda K. Evidence for line width and carrier screening effects on excitonic valley relaxation in 2D semiconductors. Nat Commun 2018; 9:2598. [PMID: 29968719 PMCID: PMC6030139 DOI: 10.1038/s41467-018-04988-x] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2017] [Accepted: 04/17/2018] [Indexed: 11/09/2022] Open
Abstract
Monolayers of transition metal dichalcogenides (TMDC) have recently emerged as excellent platforms for exploiting new physics and applications relying on electronic valley degrees of freedom in two-dimensional (2D) systems. Here, we demonstrate that Coulomb screening by 2D carriers plays a critical role in excitonic valley pseudospin relaxation processes in naturally carrier-doped WSe2 monolayers (1L-WSe2). The exciton valley relaxation times were examined using polarization- and time-resolved photoluminescence spectroscopy at temperatures ranging from 10 to 160 K. We show that the temperature-dependent exciton valley relaxation times in 1L-WSe2 under various exciton and carrier densities can be understood using a unified framework of intervalley exciton scattering via momentum-dependent long-range electron-hole exchange interactions screened by 2D carriers that depend on the carrier density and the exciton linewidth. Moreover, the developed framework was successfully applied to engineer the valley polarization of excitons in 1L-WSe2. These findings may facilitate the development of TMDC-based opto-valleytronic devices.
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Affiliation(s)
- Yuhei Miyauchi
- Institute of Advanced Energy, Kyoto University, Uji, Kyoto, 611-0011, Japan. .,Graduate School of Science, Nagoya University, Chikusa, Nagoya, 464-8602, Japan.
| | - Satoru Konabe
- Research Institute for Science and Technology, Tokyo University of Science, 6-3-1 Katsushika-ku, Tokyo, 125-8585, Japan.,Department of Chemical Science and Technology, Hosei University, Koganei, Tokyo, 184-8584, Japan
| | - Feijiu Wang
- Institute of Advanced Energy, Kyoto University, Uji, Kyoto, 611-0011, Japan.,Graduate School of Science, Nagoya University, Chikusa, Nagoya, 464-8602, Japan
| | - Wenjin Zhang
- Institute of Advanced Energy, Kyoto University, Uji, Kyoto, 611-0011, Japan
| | - Alexander Hwang
- Department of Electrical and Computer Engineering, Rice University, Houston, TX, 77005, USA.,Department of Physics, Rice University, Houston, TX, 77005, USA
| | - Yusuke Hasegawa
- Institute of Advanced Energy, Kyoto University, Uji, Kyoto, 611-0011, Japan
| | - Lizhong Zhou
- Institute of Advanced Energy, Kyoto University, Uji, Kyoto, 611-0011, Japan
| | - Shinichiro Mouri
- Institute of Advanced Energy, Kyoto University, Uji, Kyoto, 611-0011, Japan.,Department of Electrical and Electronic Engineering, Ritsumeikan University, Kusatsu, 525-8577, Japan
| | - Minglin Toh
- Department of Physics, National University of Singapore, Singapore, 117551, Singapore
| | - Goki Eda
- Department of Physics, National University of Singapore, Singapore, 117551, Singapore.,Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore, 117546, Singapore.,Department of Chemistry, National University of Singapore, Singapore, 117543, Singapore
| | - Kazunari Matsuda
- Institute of Advanced Energy, Kyoto University, Uji, Kyoto, 611-0011, Japan
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22
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Biswas S, Husek J, Londo S, Baker LR. Highly Localized Charge Transfer Excitons in Metal Oxide Semiconductors. NANO LETTERS 2018; 18:1228-1233. [PMID: 29368513 DOI: 10.1021/acs.nanolett.7b04818] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The ability to observe charge localization in photocatalytic materials on the ultrafast time scale promises to reveal important correlations between excited state electronic structure and photochemical energy conversion. Of particular interest is the ability to determine hole localization in the hybridized valence band of transition metal oxide semiconductors. Using femtosecond extreme ultraviolet reflection absorption (XUV-RA) spectroscopy we directly observe the formation of photoexcited electrons and holes in Fe2O3, Co3O4, and NiO occurring within the 100 fs instrument response. In each material, holes localize to the O 2p valence band states as probed at the O L1-edge, while electrons localize to metal 3d conduction band states on this same time scale as probed at the metal M2,3-edge. Chemical shifts at the O L1-edge enable unambiguous comparison of metal-oxygen (M-O) bond covalency. Pump flux dependent measurements show that the exciton radius is on the order of a single M-O bond length, revealing a highly localized nature of exciton in each metal oxide studied.
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Affiliation(s)
- Somnath Biswas
- Department of Chemistry and Biochemistry, The Ohio State University , Columbus, Ohio 43210, United States
| | - Jakub Husek
- Department of Chemistry and Biochemistry, The Ohio State University , Columbus, Ohio 43210, United States
| | - Stephen Londo
- Department of Chemistry and Biochemistry, The Ohio State University , Columbus, Ohio 43210, United States
| | - L Robert Baker
- Department of Chemistry and Biochemistry, The Ohio State University , Columbus, Ohio 43210, United States
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23
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Wang Z, Mak KF, Shan J. Strongly Interaction-Enhanced Valley Magnetic Response in Monolayer WSe_{2}. PHYSICAL REVIEW LETTERS 2018; 120:066402. [PMID: 29481248 DOI: 10.1103/physrevlett.120.066402] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Revised: 09/20/2017] [Indexed: 06/08/2023]
Abstract
We measure the doping dependence of the valley Zeeman splitting of the fundamental optical transitions in monolayer WSe_{2} under an out-of-plane magnetic field by optical reflection contrast and photoluminescence spectroscopy. A nonlinear valley Zeeman effect, correlated with an over fourfold enhancement in the g factor, is observed. The effect occurs when the Fermi level crosses the spin-split upper conduction band, corresponding to a change of the spin-valley degeneracy from two to four. The enhancement increases and shows no sign of saturation as the sample temperature decreases. Our result demonstrates the importance of the Coulomb interactions in the valley magnetic response of two-dimensional transition metal dichalcogenide semiconductors.
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Affiliation(s)
- Zefang Wang
- Department of Physics and Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802-6300, USA
- School of Applied and Engineering Physics and Department of Physics, Cornell University, Ithaca, New York 14853, USA
| | - Kin Fai Mak
- Department of Physics and Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802-6300, USA
- School of Applied and Engineering Physics and Department of Physics, Cornell University, Ithaca, New York 14853, USA
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA
| | - Jie Shan
- Department of Physics and Center for 2-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802-6300, USA
- School of Applied and Engineering Physics and Department of Physics, Cornell University, Ithaca, New York 14853, USA
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA
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24
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Cunningham PD, Hanbicki AT, McCreary KM, Jonker BT. Photoinduced Bandgap Renormalization and Exciton Binding Energy Reduction in WS 2. ACS NANO 2017; 11:12601-12608. [PMID: 29227085 DOI: 10.1021/acsnano.7b06885] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Strong Coulomb attraction in monolayer transition metal dichalcogenides gives rise to tightly bound excitons and many-body interactions that dominate their optoelectronic properties. However, this Coulomb interaction can be screened through control of the surrounding dielectric environment as well as through applied voltage, which provides a potential means of tuning the bandgap, exciton binding energy, and emission wavelength. Here, we directly show that the bandgap and exciton binding energy can be optically tuned by means of the intensity of the incident light. Using transient absorption spectroscopy, we identify a sub-picosecond decay component in the excited-state dynamics of WS2 that emerges for incident photon energies above the A-exciton resonance, which originates from a nonequilibrium population of charge carriers that form excitons as they cool. The generation of this charge-carrier population exhibits two distinct energy thresholds. The higher threshold is coincident with the onset of continuum states and therefore provides a direct optical means of determining both the bandgap and exciton binding energy. Using this technique, we observe a reduction in the exciton binding energy from 310 ± 30 to 220 ± 20 meV as the excitation density is increased from 3 × 1011 to 1.2 × 1012 photons/cm2. This reduction is due to dynamic dipolar screening of Coulomb interactions by excitons, which is the underlying physical process that initiates bandgap renormalization and leads to the insulator-metal transition in monolayer transition metal dichalcogenides.
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Affiliation(s)
- Paul D Cunningham
- U.S. Naval Research Laboratory , Washington, DC 20375, United States
| | - Aubrey T Hanbicki
- U.S. Naval Research Laboratory , Washington, DC 20375, United States
| | | | - Berend T Jonker
- U.S. Naval Research Laboratory , Washington, DC 20375, United States
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25
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Gao S, Yang L, Spataru CD. Interlayer Coupling and Gate-Tunable Excitons in Transition Metal Dichalcogenide Heterostructures. NANO LETTERS 2017; 17:7809-7813. [PMID: 29164895 DOI: 10.1021/acs.nanolett.7b04021] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Bilayer van der Waals (vdW) heterostructures such as MoS2/WS2 and MoSe2/WSe2 have attracted much attention recently, particularly because of their type II band alignments and the formation of interlayer exciton as the lowest-energy excitonic state. In this work, we calculate the electronic and optical properties of such heterostructures with the first-principles GW+Bethe-Salpeter Equation (BSE) method and reveal the important role of interlayer coupling in deciding the excited-state properties, including the band alignment and excitonic properties. Our calculation shows that due to the interlayer coupling, the low energy excitons can be widely tuned by a vertical gate field. In particular, the dipole oscillator strength and radiative lifetime of the lowest energy exciton in these bilayer heterostructures is varied by over an order of magnitude within a practical external gate field. We also build a simple model that captures the essential physics behind this tunability and allows the extension of the ab initio results to a large range of electric fields. Our work clarifies the physical picture of interlayer excitons in bilayer vdW heterostructures and predicts a wide range of gate-tunable excited-state properties of 2D optoelectronic devices.
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Affiliation(s)
- Shiyuan Gao
- Department of Physics, Washington University in St. Louis , St. Louis, Missouri 63136, United States
| | - Li Yang
- Department of Physics, Washington University in St. Louis , St. Louis, Missouri 63136, United States
- Institute of Materials Science and Engineering, Washington University in St. Louis , St. Louis, Missouri 63136, United States
| | - Catalin D Spataru
- Sandia National Laboratories , Livermore, California 94551, United States
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26
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Yao K, Yan A, Kahn S, Suslu A, Liang Y, Barnard ES, Tongay S, Zettl A, Borys NJ, Schuck PJ. Optically Discriminating Carrier-Induced Quasiparticle Band Gap and Exciton Energy Renormalization in Monolayer MoS_{2}. PHYSICAL REVIEW LETTERS 2017; 119:087401. [PMID: 28952768 DOI: 10.1103/physrevlett.119.087401] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Indexed: 06/07/2023]
Abstract
Optoelectronic excitations in monolayer MoS_{2} manifest from a hierarchy of electrically tunable, Coulombic free-carrier and excitonic many-body phenomena. Investigating the fundamental interactions underpinning these phenomena-critical to both many-body physics exploration and device applications-presents challenges, however, due to a complex balance of competing optoelectronic effects and interdependent properties. Here, optical detection of bound- and free-carrier photoexcitations is used to directly quantify carrier-induced changes of the quasiparticle band gap and exciton binding energies. The results explicitly disentangle the competing effects and highlight longstanding theoretical predictions of large carrier-induced band gap and exciton renormalization in two-dimensional semiconductors.
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Affiliation(s)
- Kaiyuan Yao
- Molecular Foundry Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Department of Mechanical Engineering, University of California, Berkeley, California 94720, USA
| | - Aiming Yan
- Department of Physics, University of California, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Salman Kahn
- Department of Physics, University of California, Berkeley, California 94720, USA
| | - Aslihan Suslu
- Department of Materials Science and Engineering, Arizona State University, Tempe, Arizona 85287, USA
| | - Yufeng Liang
- Molecular Foundry Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Edward S Barnard
- Molecular Foundry Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Sefaattin Tongay
- Department of Materials Science and Engineering, Arizona State University, Tempe, Arizona 85287, USA
| | - Alex Zettl
- Department of Physics, University of California, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Kavli Energy NanoSciences Institute at the University of California, Berkeley and the Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Nicholas J Borys
- Molecular Foundry Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Department of Physics, Montana State University, Bozeman, Montana 59717, USA
| | - P James Schuck
- Molecular Foundry Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, USA
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27
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Lee B, Liu W, Naylor CH, Park J, Malek SC, Berger JS, Johnson ATC, Agarwal R. Electrical Tuning of Exciton-Plasmon Polariton Coupling in Monolayer MoS 2 Integrated with Plasmonic Nanoantenna Lattice. NANO LETTERS 2017; 17:4541-4547. [PMID: 28613887 DOI: 10.1021/acs.nanolett.7b02245] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Active control of light-matter interactions in semiconductors is critical for realizing next generation optoelectronic devices with real-time control of the system's optical properties and hence functionalities via external fields. The ability to dynamically manipulate optical interactions by applied fields in active materials coupled to cavities with fixed geometrical parameters opens up possibilities of controlling the lifetimes, oscillator strengths, effective mass, and relaxation properties of a coupled exciton-photon (or plasmon) system. Here, we demonstrate electrical control of exciton-plasmon coupling strengths between strong and weak coupling limits in a two-dimensional semiconductor integrated with plasmonic nanoresonators assembled in a field-effect transistor device by electrostatic doping. As a result, the energy-momentum dispersions of such an exciton-plasmon coupled system can be altered dynamically with applied electric field by modulating the excitonic properties of monolayer MoS2 arising from many-body effects. In addition, evidence of enhanced coupling between charged excitons (trions) and plasmons was also observed upon increased carrier injection, which can be utilized for fabricating Fermionic polaritonic and magnetoplasmonic devices. The ability to dynamically control the optical properties of a coupled exciton-plasmonic system with electric fields demonstrates the versatility of the coupled system and offers a new platform for the design of optoelectronic devices with precisely tailored responses.
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Affiliation(s)
- Bumsu Lee
- Department of Materials Science and Engineering and ‡Department of Physics and Astronomy, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States
| | - Wenjing Liu
- Department of Materials Science and Engineering and ‡Department of Physics and Astronomy, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States
| | - Carl H Naylor
- Department of Materials Science and Engineering and ‡Department of Physics and Astronomy, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States
| | - Joohee Park
- Department of Materials Science and Engineering and ‡Department of Physics and Astronomy, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States
| | - Stephanie C Malek
- Department of Materials Science and Engineering and ‡Department of Physics and Astronomy, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States
| | - Jacob S Berger
- Department of Materials Science and Engineering and ‡Department of Physics and Astronomy, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States
| | - A T Charlie Johnson
- Department of Materials Science and Engineering and ‡Department of Physics and Astronomy, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States
| | - Ritesh Agarwal
- Department of Materials Science and Engineering and ‡Department of Physics and Astronomy, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States
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28
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Cao Z, Harb M, Lardhi S, Cavallo L. Impact of Interfacial Defects on the Properties of Monolayer Transition Metal Dichalcogenide Lateral Heterojunctions. J Phys Chem Lett 2017; 8:1664-1669. [PMID: 28332394 DOI: 10.1021/acs.jpclett.7b00518] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We explored the impact of interfacial defects on the stability and optoelectronic properties of monolayer transition metal dichalcogenide lateral heterojunctions using a density functional theory approach. As a prototype, we focused on the MoS2-WSe2 system and found that even a random alloy-like interface with a width of less than 1 nm has only a minimal impact on the band gap and alignment compared to the defect-less interface. The largest impact is on the evolution of the electrostatic potential across the monolayer. Similar to defect-less interfaces, a small number of defects results in an electrostatic potential profile with a sharp change at the interface, which facilitates exciton dissociation. Differently, a large number of defects results in an electrostatic potential profile switching smoothly across the interface, which is expected to reduce the capability of the heterojunction to promote exciton dissociation. These results are generalizable to other transition metal dichalcogenide lateral heterojunctions.
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Affiliation(s)
- Zhen Cao
- King Abdullah University of Science and Technology (KAUST), KAUST Catalysis Center (KCC), Physical Sciences and Engineering Division (PSE), Thuwal 23955-6900, Saudi Arabia
| | - Moussab Harb
- King Abdullah University of Science and Technology (KAUST), KAUST Catalysis Center (KCC), Physical Sciences and Engineering Division (PSE), Thuwal 23955-6900, Saudi Arabia
| | - Sheikha Lardhi
- King Abdullah University of Science and Technology (KAUST), KAUST Catalysis Center (KCC), Physical Sciences and Engineering Division (PSE), Thuwal 23955-6900, Saudi Arabia
| | - Luigi Cavallo
- King Abdullah University of Science and Technology (KAUST), KAUST Catalysis Center (KCC), Physical Sciences and Engineering Division (PSE), Thuwal 23955-6900, Saudi Arabia
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29
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Wang Z, Zhao L, Mak KF, Shan J. Probing the Spin-Polarized Electronic Band Structure in Monolayer Transition Metal Dichalcogenides by Optical Spectroscopy. NANO LETTERS 2017; 17:740-746. [PMID: 28103668 DOI: 10.1021/acs.nanolett.6b03855] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We study the electronic band structure in the K/K' valleys of the Brillouin zone of monolayer WSe2 and MoSe2 by optical reflection and photoluminescence spectroscopy on dual-gated field-effect devices. Our experiment reveals the distinct spin polarization in the conduction bands of these compounds by a systematic study of the doping dependence of the A and B excitonic resonances. Electrons in the highest-energy valence band and the lowest-energy conduction band have antiparallel spins in monolayer WSe2 and parallel spins in monolayer MoSe2. The spin splitting is determined to be hundreds of meV for the valence bands and tens of meV for the conduction bands, which are in good agreement with first-principles calculations. These values also suggest that both n- and p-type WSe2 and MoSe2 can be relevant for spin- and valley-based applications.
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Affiliation(s)
- Zefang Wang
- Department of Physics and Center for 2-Dimensional and Layered Materials, The Pennsylvania State University , University Park, Pennsylvania 16802-6300, United States
| | - Liang Zhao
- Department of Physics, Case Western Reserve University , Cleveland, Ohio 44106-7079, United States
| | - Kin Fai Mak
- Department of Physics and Center for 2-Dimensional and Layered Materials, The Pennsylvania State University , University Park, Pennsylvania 16802-6300, United States
| | - Jie Shan
- Department of Physics and Center for 2-Dimensional and Layered Materials, The Pennsylvania State University , University Park, Pennsylvania 16802-6300, United States
- Department of Physics, Case Western Reserve University , Cleveland, Ohio 44106-7079, United States
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30
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Cunningham PD, McCreary KM, Jonker BT. Auger Recombination in Chemical Vapor Deposition-Grown Monolayer WS 2. J Phys Chem Lett 2016; 7:5242-5246. [PMID: 27973899 DOI: 10.1021/acs.jpclett.6b02413] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Reduced dimensionality and strong Coulombic interactions in monolayer semiconductors lead to enhanced many-body interactions. Here, we report Auger recombination, i.e., exciton-exciton annihilation, in large-area chemical vapor deposition-grown monolayer WS2. Using ultrafast spectroscopy, we experimentally determine the Auger rate to be 0.089 ± 0.001 cm2/s at room temperature, which is an order of magnitude greater than the bulk value. This nonradiative recombination pathway dominates, regardless of excitation energy, for exciton densities greater than 8.0 ± 0.6 × 1010 cm-2 and below the Mott density. Higher-energy excitation above the A exciton resonance may initially produce a hot electron-hole gas that precedes exciton formation. Therefore, we use resonant excitation of the A exciton to ensure accuracy and avoid artifacts associated with other photogenerated species.
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Affiliation(s)
- Paul D Cunningham
- U.S. Naval Research Laboratory , Washington, D.C. 20375, United States
| | | | - Berend T Jonker
- U.S. Naval Research Laboratory , Washington, D.C. 20375, United States
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