1
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Brotons-Gisbert M, Gerardot BD, Holleitner AW, Wurstbauer U. Interlayer and Moiré excitons in atomically thin double layers: From individual quantum emitters to degenerate ensembles. MRS BULLETIN 2024; 49:914-931. [PMID: 39247683 PMCID: PMC11379794 DOI: 10.1557/s43577-024-00772-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Accepted: 07/13/2024] [Indexed: 09/10/2024]
Abstract
Abstract Interlayer excitons (IXs), composed of electron and hole states localized in different layers, excel in bilayers composed of atomically thin van der Waals materials such as semiconducting transition-metal dichalcogenides (TMDs) due to drastically enlarged exciton binding energies, exciting spin-valley properties, elongated lifetimes, and large permanent dipoles. The latter allows modification by electric fields and the study of thermalized bosonic quasiparticles, from the single particle level to interacting degenerate dense ensembles. Additionally, the freedom to combine bilayers of different van der Waals materials without lattice or relative twist-angle constraints leads to layer-hybridized and Moiré excitons, which can be widely engineered. This article covers fundamental aspects of IXs, including correlation phenomena as well as the consequence of Moiré superlattices with a strong focus on TMD homo- and heterobilayers. Graphical abstract
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Affiliation(s)
- Mauro Brotons-Gisbert
- Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh, UK
| | - Brian D Gerardot
- Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh, UK
| | - Alexander W Holleitner
- Walter Schottky Institute and Physics Department, Technical University of Munich, Garching, Germany
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2
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Jash A, Stern M, Misra S, Umansky V, Joseph IB. Giant hyperfine interaction between a dark exciton condensate and nuclei. SCIENCE ADVANCES 2024; 10:eado8763. [PMID: 39151004 PMCID: PMC11328897 DOI: 10.1126/sciadv.ado8763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2024] [Accepted: 07/11/2024] [Indexed: 08/18/2024]
Abstract
We study the interaction of a dark exciton Bose-Einstein condensate with the nuclei in gallium arsenide/aluminum gallium arsenide coupled quantum wells and find clear evidence for nuclear polarization buildup that accompanies the appearance of the condensate. We show that the nuclei are polarized throughout the mesa area, extending to regions that are far away from the photoexcitation area and persisting for seconds after the excitation is switched off. Photoluminescence measurements in the presence of radio frequency radiation reveal that the hyperfine interaction between the nuclear and electron spins is enhanced by two orders of magnitude. We suggest that this large enhancement manifests the collective nature of the N-exciton condensate, which amplifies the interaction by a factor of [Formula: see text].
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Affiliation(s)
- Amit Jash
- Department of Condensed Matter physics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Michael Stern
- Department of Physics, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Subhradeep Misra
- Department of Condensed Matter physics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Vladimir Umansky
- Department of Condensed Matter physics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Israel Bar Joseph
- Department of Condensed Matter physics, Weizmann Institute of Science, Rehovot 7610001, Israel
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3
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Joe AY, Mier Valdivia AM, Jauregui LA, Pistunova K, Ding D, Zhou Y, Scuri G, De Greve K, Sushko A, Kim B, Taniguchi T, Watanabe K, Hone JC, Lukin MD, Park H, Kim P. Controlled interlayer exciton ionization in an electrostatic trap in atomically thin heterostructures. Nat Commun 2024; 15:6743. [PMID: 39112505 PMCID: PMC11306233 DOI: 10.1038/s41467-024-51128-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2024] [Accepted: 07/30/2024] [Indexed: 08/10/2024] Open
Abstract
Atomically thin semiconductor heterostructures provide a two-dimensional (2D) device platform for creating high densities of cold, controllable excitons. Interlayer excitons (IEs), bound electrons and holes localized to separate 2D quantum well layers, have permanent out-of-plane dipole moments and long lifetimes, allowing their spatial distribution to be tuned on demand. Here, we employ electrostatic gates to trap IEs and control their density. By electrically modulating the IE Stark shift, electron-hole pair concentrations above 2 × 1012 cm-2 can be achieved. At this high IE density, we observe an exponentially increasing linewidth broadening indicative of an IE ionization transition, independent of the trap depth. This runaway threshold remains constant at low temperatures, but increases above 20 K, consistent with the quantum dissociation of a degenerate IE gas. Our demonstration of the IE ionization in a tunable electrostatic trap represents an important step towards the realization of dipolar exciton condensates in solid-state optoelectronic devices.
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Affiliation(s)
- Andrew Y Joe
- Department of Physics, Harvard University, Cambridge, MA, USA
- Department of Physics and Astronomy, University of California, Riverside, CA, USA
| | - Andrés M Mier Valdivia
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - Luis A Jauregui
- Department of Physics, University of California, Irvine, CA, USA
| | | | - Dapeng Ding
- Department of Physics, Harvard University, Cambridge, MA, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
| | - You Zhou
- Department of Physics, Harvard University, Cambridge, MA, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
- Department of Materials Science and Engineering, University of Maryland, College Park, MD, USA
| | - Giovanni Scuri
- Department of Physics, Harvard University, Cambridge, MA, USA
- E. L. Ginzton Laboratory, Stanford University, Stanford, CA, USA
| | - Kristiaan De Greve
- Department of Physics, Harvard University, Cambridge, MA, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
| | - Andrey Sushko
- Department of Physics, Harvard University, Cambridge, MA, USA
| | - Bumho Kim
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Japan
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Japan
| | - James C Hone
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - Mikhail D Lukin
- Department of Physics, Harvard University, Cambridge, MA, USA
| | - Hongkun Park
- Department of Physics, Harvard University, Cambridge, MA, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
| | - Philip Kim
- Department of Physics, Harvard University, Cambridge, MA, USA.
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA.
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4
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Liu H, Wang J, Chen S, Sun Z, Xu H, Han Y, Wang C, Liu H, Huang L, Luo J, Liu D. Direct Visualization of Dark Interlayer Exciton Transport in Moiré Superlattices. NANO LETTERS 2024; 24:339-346. [PMID: 38147355 DOI: 10.1021/acs.nanolett.3c04105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2023]
Abstract
Moiré superlattices have emerged as an unprecedented manipulation tool for engineering correlated quantum phenomena in van der Waals heterostructures. With moiré potentials as a naturally configurable solid-state that sustains high exciton density, interlayer excitons in transition metal dichalcogenide heterostructures are expected to achieve high-temperature exciton condensation. However, the exciton degeneracy state is usually optically inactive due to the finite momentum of interlayer excitons. Experimental observation of dark interlayer excitons in moiré potentials remains challenging. Here we directly visualize the dark interlayer exciton transport in WS2/h-BN/WSe2 heterostructures using femtosecond transient absorption microscopy. We observe a transition from classical free exciton gas to quantum degeneracy by imaging temperature-dependent exciton transport. Below a critical degeneracy temperature, exciton diffusion rates exhibit an accelerating downward trend, which can be explained well by a nonlinear quantum diffusion model. These results open the door to quantum information processing and high-precision metrology in moiré superlattices.
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Affiliation(s)
- Huan Liu
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
| | - Jiangcai Wang
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
| | - Shihong Chen
- School of Resources, Environment and Materials, Guangxi University, Nanning 530004, China
| | - Zejun Sun
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
| | - Haowen Xu
- Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing 100083, China
| | - Yishu Han
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
| | - Chong Wang
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
| | - Huixian Liu
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
| | - Li Huang
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
| | - Jianbin Luo
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
| | - Dameng Liu
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
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5
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Lee H, Kim YB, Ryu JW, Kim S, Bae J, Koo Y, Jang D, Park KD. Recent progress of exciton transport in two-dimensional semiconductors. NANO CONVERGENCE 2023; 10:57. [PMID: 38102309 PMCID: PMC10724105 DOI: 10.1186/s40580-023-00404-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Accepted: 11/20/2023] [Indexed: 12/17/2023]
Abstract
Spatial manipulation of excitonic quasiparticles, such as neutral excitons, charged excitons, and interlayer excitons, in two-dimensional semiconductors offers unique capabilities for a broad range of optoelectronic applications, encompassing photovoltaics, exciton-integrated circuits, and quantum light-emitting systems. Nonetheless, their practical implementation is significantly restricted by the absence of electrical controllability for neutral excitons, short lifetime of charged excitons, and low exciton funneling efficiency at room temperature, which remain a challenge in exciton transport. In this comprehensive review, we present the latest advancements in controlling exciton currents by harnessing the advanced techniques and the unique properties of various excitonic quasiparticles. We primarily focus on four distinct control parameters inducing the exciton current: electric fields, strain gradients, surface plasmon polaritons, and photonic cavities. For each approach, the underlying principles are introduced in conjunction with its progression through recent studies, gradually expanding their accessibility, efficiency, and functionality. Finally, we outline the prevailing challenges to fully harness the potential of excitonic quasiparticles and implement practical exciton-based optoelectronic devices.
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Affiliation(s)
- Hyeongwoo Lee
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea
| | - Yong Bin Kim
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea
| | - Jae Won Ryu
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea
| | - Sujeong Kim
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea
| | - Jinhyuk Bae
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea
| | - Yeonjeong Koo
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea
| | - Donghoon Jang
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea
| | - Kyoung-Duck Park
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea.
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6
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Ambrosetti A, Silvestrelli PL, Salasnich L. Superfluidity Meets the Solid State: Frictionless Mass Transport through a (5,5) Carbon Nanotube. PHYSICAL REVIEW LETTERS 2023; 131:206301. [PMID: 38039458 DOI: 10.1103/physrevlett.131.206301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Accepted: 10/17/2023] [Indexed: 12/03/2023]
Abstract
Superfluidity is a well-characterized quantum phenomenon which entails frictionless motion of mesoscopic particles through a superfluid, such as ^{4}He or dilute atomic gases at very low temperatures. As shown by Landau, the incompatibility between energy and momentum conservation, which ultimately stems from the spectrum of the elementary excitations of the superfluid, forbids quantum scattering between the superfluid and the moving mesoscopic particle, below a critical speed threshold. Here, we predict that frictionless motion can also occur in the absence of a standard superfluid, i.e., when a He atom travels through a narrow (5,5) carbon nanotube (CNT). Because of the quasilinear dispersion of the plasmon and phonon modes that could interact with He, the (5,5) CNT embodies a solid-state analog of the superfluid, thereby enabling straightforward transfer of Landau's criterion of superfluidity. As a result, Landau's equations acquire broader generality and may be applicable to other nanoscale friction phenomena, whose description has been so far purely classical.
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Affiliation(s)
- Alberto Ambrosetti
- Dipartimento di Fisica e Astronomia, Università degli Studi di Padova, via Marzolo 8, 35131 Padova, Italy
| | - Pier Luigi Silvestrelli
- Dipartimento di Fisica e Astronomia, Università degli Studi di Padova, via Marzolo 8, 35131 Padova, Italy
| | - Luca Salasnich
- Dipartimento di Fisica e Astronomia, Università degli Studi di Padova, via Marzolo 8, 35131 Padova, Italy
- Istituto Nazionale di Fisica Nucleare, Sezione di Padova, via Marzolo 8, 35131 Padova, Italy and Istituto Nazionale di Ottica del Consiglio Nazionale delle Ricerche, Unità di Sesto Fiorentino, via Carrara 1, 50019 Sesto Fiorentino (Firenze), Italy
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7
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Troue M, Figueiredo J, Sigl L, Paspalides C, Katzer M, Taniguchi T, Watanabe K, Selig M, Knorr A, Wurstbauer U, Holleitner AW. Extended Spatial Coherence of Interlayer Excitons in MoSe_{2}/WSe_{2} Heterobilayers. PHYSICAL REVIEW LETTERS 2023; 131:036902. [PMID: 37540866 DOI: 10.1103/physrevlett.131.036902] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Accepted: 06/09/2023] [Indexed: 08/06/2023]
Abstract
We report on the spatial coherence of interlayer exciton ensembles as formed in MoSe_{2}/WSe_{2} heterostructures and characterized by point-inversion Michelson-Morley interferometry. Below 10 K, the measured spatial coherence length of the interlayer excitons reaches values equivalent to the lateral expansion of the exciton ensembles. In this regime, the light emission of the excitons turns out to be homogeneously broadened in energy with a high temporal coherence. At higher temperatures, both the spatial coherence length and the temporal coherence time decrease, most likely because of thermal processes. The presented findings point towards a spatially extended, coherent many-body state of interlayer excitons at low temperature.
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Affiliation(s)
- Mirco Troue
- Walter Schottky Institute and Physics Department, Technical University of Munich, Am Coulombwall 4a, 85748 Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), Schellingstr. 4, 80799 Munich, Germany
| | - Johannes Figueiredo
- Walter Schottky Institute and Physics Department, Technical University of Munich, Am Coulombwall 4a, 85748 Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), Schellingstr. 4, 80799 Munich, Germany
| | - Lukas Sigl
- Walter Schottky Institute and Physics Department, Technical University of Munich, Am Coulombwall 4a, 85748 Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), Schellingstr. 4, 80799 Munich, Germany
| | - Christos Paspalides
- Walter Schottky Institute and Physics Department, Technical University of Munich, Am Coulombwall 4a, 85748 Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), Schellingstr. 4, 80799 Munich, Germany
| | - Manuel Katzer
- Institute for Theoretical Physics, Nonlinear Optics and Quantum Electronics, Technical University of Berlin, 10623 Berlin, Germany
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Malte Selig
- Institute for Theoretical Physics, Nonlinear Optics and Quantum Electronics, Technical University of Berlin, 10623 Berlin, Germany
| | - Andreas Knorr
- Institute for Theoretical Physics, Nonlinear Optics and Quantum Electronics, Technical University of Berlin, 10623 Berlin, Germany
| | - Ursula Wurstbauer
- Institute of Physics, Münster University, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
| | - Alexander W Holleitner
- Walter Schottky Institute and Physics Department, Technical University of Munich, Am Coulombwall 4a, 85748 Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), Schellingstr. 4, 80799 Munich, Germany
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8
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Zheng W, Xiang L, de Quesada FA, Augustin M, Lu Z, Wilson M, Sood A, Wu F, Shcherbakov D, Memaran S, Baumbach RE, McCandless GT, Chan JY, Liu S, Edgar JH, Lau CN, Lui CH, Santos EJG, Lindenberg A, Smirnov D, Balicas L. Thickness- and Twist-Angle-Dependent Interlayer Excitons in Metal Monochalcogenide Heterostructures. ACS NANO 2022; 16:18695-18707. [PMID: 36257051 DOI: 10.1021/acsnano.2c07394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Interlayer excitons, or bound electron-hole pairs whose constituent quasiparticles are located in distinct stacked semiconducting layers, are being intensively studied in heterobilayers of two-dimensional semiconductors. They owe their existence to an intrinsic type-II band alignment between both layers that convert these into p-n junctions. Here, we unveil a pronounced interlayer exciton (IX) in heterobilayers of metal monochalcogenides, namely, γ-InSe on ε-GaSe, whose pronounced emission is adjustable just by varying their thicknesses given their number of layers dependent direct band gaps. Time-dependent photoluminescense spectroscopy unveils considerably longer interlayer exciton lifetimes with respect to intralayer ones, thus confirming their nature. The linear Stark effect yields a bound electron-hole pair whose separation d is just (3.6 ± 0.1) Å with d being very close to dSe = 3.4 Å which is the calculated interfacial Se separation. The envelope of IX is twist-angle-dependent and describable by superimposed emissions that are nearly equally spaced in energy, as if quantized due to localization induced by the small moiré periodicity. These heterostacks are characterized by extremely flat interfacial valence bands making them prime candidates for the observation of magnetism or other correlated electronic phases upon carrier doping.
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Affiliation(s)
- Wenkai Zheng
- National High Magnetic Field Laboratory, Tallahassee, Florida32310, United States
- Department of Physics, Florida State University, Tallahassee, Florida32306, United States
| | - Li Xiang
- National High Magnetic Field Laboratory, Tallahassee, Florida32310, United States
- Department of Physics, Florida State University, Tallahassee, Florida32306, United States
| | - Felipe A de Quesada
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California94025, United States
- Department of Materials Science and Engineering, Stanford University, Stanford, California94305, United States
| | - Mathias Augustin
- Institute for Condensed Matter Physics and Complex Systems, School of Physics and Astronomy, The University of Edinburgh, EdinburghEH9 3FD, United Kingdom
- Higgs Centre for Theoretical Physics, The University of Edinburgh, EdinburghEH9 3FD, United Kingdom
| | - Zhengguang Lu
- National High Magnetic Field Laboratory, Tallahassee, Florida32310, United States
- Department of Physics, Florida State University, Tallahassee, Florida32306, United States
| | - Matthew Wilson
- Department of Physics and Astronomy, University of California, Riverside, California92521, United States
| | - Aditya Sood
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California94025, United States
- Department of Materials Science and Engineering, Stanford University, Stanford, California94305, United States
| | - Fengcheng Wu
- School of Physics and Technology, Wuhan University, Wuhan, 430072China
| | - Dmitry Shcherbakov
- Department of Physics, The Ohio State University, Columbus, Ohio43210, United States
| | - Shahriar Memaran
- National High Magnetic Field Laboratory, Tallahassee, Florida32310, United States
- Department of Physics, Florida State University, Tallahassee, Florida32306, United States
| | - Ryan E Baumbach
- National High Magnetic Field Laboratory, Tallahassee, Florida32310, United States
- Department of Physics, Florida State University, Tallahassee, Florida32306, United States
| | - Gregory T McCandless
- Department of Chemistry and Biochemistry, Baylor University, Waco, Texas76798, United States
| | - Julia Y Chan
- Department of Chemistry and Biochemistry, Baylor University, Waco, Texas76798, United States
| | - Song Liu
- Tim Taylor Department of Chemical Engineering, Kansas State University, Manhattan, Kansas66506, United States
| | - James H Edgar
- Tim Taylor Department of Chemical Engineering, Kansas State University, Manhattan, Kansas66506, United States
| | - Chun Ning Lau
- Department of Physics, The Ohio State University, Columbus, Ohio43210, United States
| | - Chun Hung Lui
- Department of Physics and Astronomy, University of California, Riverside, California92521, United States
| | - Elton J G Santos
- Institute for Condensed Matter Physics and Complex Systems, School of Physics and Astronomy, The University of Edinburgh, EdinburghEH9 3FD, United Kingdom
- Higgs Centre for Theoretical Physics, The University of Edinburgh, EdinburghEH9 3FD, United Kingdom
- Donostia International Physics Centre, 20018Donostia-San Sebastian, Spain
| | - Aaron Lindenberg
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California94025, United States
- Department of Materials Science and Engineering, Stanford University, Stanford, California94305, United States
| | - Dmitry Smirnov
- National High Magnetic Field Laboratory, Tallahassee, Florida32310, United States
| | - Luis Balicas
- National High Magnetic Field Laboratory, Tallahassee, Florida32310, United States
- Department of Physics, Florida State University, Tallahassee, Florida32306, United States
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9
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Wrona PR, Rabani E, Geissler PL. A Pair of 2D Quantum Liquids: Investigating the Phase Behavior of Indirect Excitons. ACS NANO 2022; 16:15339-15346. [PMID: 36069715 PMCID: PMC9527805 DOI: 10.1021/acsnano.2c06947] [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: 07/13/2022] [Accepted: 09/01/2022] [Indexed: 06/15/2023]
Abstract
Long-lived indirect excitons (IXs) exhibit a rich phase diagram, including a Bose-Einstein condensate (BEC), a Wigner crystal, and other exotic phases. Recent experiments have hinted at a "classical" liquid of IXs above the BEC transition. To uncover the nature of this phase, we use a broad range of theoretical tools and find no evidence of a driving force toward classical condensation. Instead, we attribute the condensed phase to a quantum electron-hole liquid (EHL), first proposed by Keldysh for direct excitons. Taking into account the association of free carriers into bound excitons, we study the phase equilibrium between a gas of excitons, a gas of free carriers, and an EHL for a wide range of electron-hole separations, temperatures, densities, and mass ratios. Our results agree reasonably well with recent measurements of GaAs/AlGaAs coupled quantum wells.
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Affiliation(s)
- Paul R. Wrona
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
| | - Eran Rabani
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
- Materials
Sciences Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
- The
Raymond and Beverly Sackler Center of Computational Molecular and
Materials Science, Tel Aviv University, Tel Aviv 69978, Israel
| | - Phillip L. Geissler
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
- Materials
Sciences Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
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10
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Morita Y, Yoshioka K, Kuwata-Gonokami M. Observation of Bose-Einstein condensates of excitons in a bulk semiconductor. Nat Commun 2022; 13:5388. [PMID: 36104375 PMCID: PMC9474864 DOI: 10.1038/s41467-022-33103-4] [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: 05/21/2021] [Accepted: 08/31/2022] [Indexed: 11/25/2022] Open
Abstract
An unambiguous observation of the Bose-Einstein condensation (BEC) of excitons in a photoexcited bulk semiconductor and elucidation of its inherent nature have been longstanding problems in condensed matter physics. Here, we observe the quantum phase transition and a Bose-Einstein condensate appearing in a trapped gas of 1s paraexcitons in bulk Cu2O below 400 mK, by directly visualizing the exciton cloud in real space using mid-infrared induced absorption imaging that we realized in a dilution refrigerator. Our study shows that the paraexciton condensate is undetectable by conventional luminescence spectroscopy. We find an unconventionally small condensate fraction of 0.016 with the spatial profile of the condensate well described by mean-field theory. Our discovery of this new type of BEC in the purely matter-like exciton system interacting with a cold phonon bath could pave the way for the classification of its long-range order, and for essential understanding of quantum statistical mechanics of non-equilibrium open systems. Bose-Einstein condensate of excitons is expected in photo-excited bulk semiconductors, but a direct experimental evidence has been lacking. Here the authors report the observation of a condensate of 1s paraexcitons in Cu2O using real-space mid-infrared absorption imaging realized in a dilution refrigerator.
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11
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Slobodkin Y, Mazuz-Harpaz Y, Refaely-Abramson S, Gazit S, Steinberg H, Rapaport R. Quantum Phase Transitions of Trilayer Excitons in Atomically Thin Heterostructures. PHYSICAL REVIEW LETTERS 2020; 125:255301. [PMID: 33416340 DOI: 10.1103/physrevlett.125.255301] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 11/17/2020] [Indexed: 06/12/2023]
Abstract
We determine the phase diagram of excitons in a symmetric transition-metal dichalcogenide 3-layer heterostructure. First principles calculations reveal interlayer exciton states of a symmetric quadrupole, from which higher energy asymmetric dipole states are composed. We find quantum phase transitions between a repulsive quadrupolar and an attractive staggered dipolar lattice phases, driven by a competition between interactions and single exciton energies. The different internal quantum state of excitons in each phase is a striking example of a system where single-particle and interacting many-body states are coupled.
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Affiliation(s)
- Yevgeny Slobodkin
- The Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
| | - Yotam Mazuz-Harpaz
- The Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
| | - Sivan Refaely-Abramson
- Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Snir Gazit
- The Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
- The Fritz Haber Research Center for Molecular Dynamics, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
| | - Hadar Steinberg
- The Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
| | - Ronen Rapaport
- The Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
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12
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Calman EV, Fowler-Gerace LH, Choksy DJ, Butov LV, Nikonov DE, Young IA, Hu S, Mishchenko A, Geim AK. Indirect Excitons and Trions in MoSe 2/WSe 2 van der Waals Heterostructures. NANO LETTERS 2020; 20:1869-1875. [PMID: 32069058 DOI: 10.1021/acs.nanolett.9b05086] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Indirect excitons (IX) in semiconductor heterostructures are bosons, which can cool below the temperature of quantum degeneracy and can be effectively controlled by voltage and light. IX quantum Bose gases and IX devices were explored in GaAs heterostructures where an IX range of existence is limited to low temperatures due to low IX binding energies. IXs in van der Waals transition-metal dichalcogenide (TMD) heterostructures are characterized by large binding energies giving the opportunity for exploring excitonic quantum gases and for creating excitonic devices at high temperatures. TMD heterostructures also offer a new platform for studying single-exciton phenomena and few-particle complexes. In this work, we present studies of IXs in MoSe2/WSe2 heterostructures and report on two IX luminescence lines whose energy splitting and temperature dependence identify them as neutral and charged IXs. The experimentally found binding energy of the indirect charged excitons, that is, indirect trions, is close to the calculated binding energy of 28 meV for negative indirect trions in TMD heterostructures [Deilmann, T.; Thygesen, K. S. Nano Lett. 2018, 18, 1460]. We also report on the realization of IXs with a luminescence line width reaching 4 meV at low temperatures. An enhancement of IX luminescence intensity and the narrow line width are observed in localized spots.
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Affiliation(s)
- E V Calman
- Department of Physics, University of California at San Diego, La Jolla, California 92093, United States
| | - L H Fowler-Gerace
- Department of Physics, University of California at San Diego, La Jolla, California 92093, United States
| | - D J Choksy
- Department of Physics, University of California at San Diego, La Jolla, California 92093, United States
| | - L V Butov
- Department of Physics, University of California at San Diego, La Jolla, California 92093, United States
| | - D E Nikonov
- Components Research, Intel Corporation, Hillsboro, Oregon 97124 United States
| | - I A Young
- Components Research, Intel Corporation, Hillsboro, Oregon 97124 United States
| | - S Hu
- School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
| | - A Mishchenko
- School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
| | - A K Geim
- School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
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13
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Huang XX, Claassen M, Huang EW, Moritz B, Devereaux TP. Biexciton Condensation in Electron-Hole-Doped Hubbard Bilayers: A Sign-Problem-Free Quantum Monte Carlo Study. PHYSICAL REVIEW LETTERS 2020; 124:077601. [PMID: 32142325 DOI: 10.1103/physrevlett.124.077601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Accepted: 01/14/2020] [Indexed: 06/10/2023]
Abstract
The bilayer Hubbard model with electron-hole doping is an ideal platform to study excitonic orders due to suppressed recombination via spatial separation of electrons and holes. However, suffering from the sign problem, previous quantum Monte Carlo studies could not arrive at an unequivocal conclusion regarding the presence of phases with clear signatures of excitonic condensation in bilayer Hubbard models. Here, we develop a determinant quantum Monte Carlo algorithm for the bilayer Hubbard model that is sign-problem-free for equal and opposite doping in the two layers and study excitonic order and charge and spin density modulations as a function of chemical potential difference between the two layers, on-site Coulomb repulsion, and interlayer interaction. In the intermediate coupling regime and in proximity to the SU(4)-symmetric point, we find a biexcitonic condensate phase at finite electron-hole doping, as well as a competing (π,π) charge density wave state. We extract the Berezinskii-Kosterlitz-Thouless transition temperature from superfluid density and a finite-size scaling analysis of the correlation functions and explain our results in terms of an effective biexcitonic hard-core boson model.
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Affiliation(s)
- Xu-Xin Huang
- Department of Applied Physics, Stanford University, Stanford, California 94305, USA
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory and Stanford University, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - Martin Claassen
- Center for Computational Quantum Physics, Flatiron Institute, Simons Foundation, 162 5th Avenue, New York, New York 10010, USA
| | - Edwin W Huang
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory and Stanford University, 2575 Sand Hill Road, Menlo Park, California 94025, USA
- Department of Physics, Stanford University, Stanford, California 94305, USA
| | - Brian Moritz
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory and Stanford University, 2575 Sand Hill Road, Menlo Park, California 94025, USA
- Department of Physics and Astrophysics, University of North Dakota, Grand Forks, North Dakota 58202, USA
| | - Thomas P Devereaux
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory and Stanford University, 2575 Sand Hill Road, Menlo Park, California 94025, USA
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA
- Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA
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14
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Jauregui LA, Joe AY, Pistunova K, Wild DS, High AA, Zhou Y, Scuri G, De Greve K, Sushko A, Yu CH, Taniguchi T, Watanabe K, Needleman DJ, Lukin MD, Park H, Kim P. Electrical control of interlayer exciton dynamics in atomically thin heterostructures. Science 2019; 366:870-875. [DOI: 10.1126/science.aaw4194] [Citation(s) in RCA: 156] [Impact Index Per Article: 31.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Accepted: 10/18/2019] [Indexed: 12/15/2022]
Abstract
A van der Waals heterostructure built from atomically thin semiconducting transition metal dichalcogenides (TMDs) enables the formation of excitons from electrons and holes in distinct layers, producing interlayer excitons with large binding energy and a long lifetime. By employing heterostructures of monolayer TMDs, we realize optical and electrical generation of long-lived neutral and charged interlayer excitons. We demonstrate that neutral interlayer excitons can propagate across the entire sample and that their propagation can be controlled by excitation power and gate electrodes. We also use devices with ohmic contacts to facilitate the drift motion of charged interlayer excitons. The electrical generation and control of excitons provide a route for achieving quantum manipulation of bosonic composite particles with complete electrical tunability.
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Affiliation(s)
| | - Andrew Y. Joe
- Department of Physics, Harvard University, Cambridge, MA, USA
| | | | - Dominik S. Wild
- Department of Physics, Harvard University, Cambridge, MA, USA
| | - Alexander A. High
- Department of Physics, Harvard University, Cambridge, MA, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
| | - You Zhou
- Department of Physics, Harvard University, Cambridge, MA, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
| | - Giovanni Scuri
- Department of Physics, Harvard University, Cambridge, MA, USA
| | - Kristiaan De Greve
- Department of Physics, Harvard University, Cambridge, MA, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
| | - Andrey Sushko
- Department of Physics, Harvard University, Cambridge, MA, USA
| | - Che-Hang Yu
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - Takashi Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, Japan
| | - Kenji Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, Japan
| | - Daniel J. Needleman
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, USA
- Faculty of Arts and Sciences Center for Systems Biology, Harvard University, Cambridge, MA, USA
| | | | - Hongkun Park
- Department of Physics, Harvard University, Cambridge, MA, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
| | - Philip Kim
- Department of Physics, Harvard University, Cambridge, MA, USA
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
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15
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Dynamical formation of a strongly correlated dark condensate of dipolar excitons. Proc Natl Acad Sci U S A 2019; 116:18328-18333. [PMID: 31451654 DOI: 10.1073/pnas.1903374116] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Strongly interacting bosons display a rich variety of quantum phases, the study of which has so far been focused in the dilute regime, at a fixed number of particles. Here we demonstrate the formation of a dense Bose-Einstein condensate in a long-lived dark spin state of 2D dipolar excitons. A dark condensate of weakly interacting excitons is very fragile, being unstable against a coherent coupling of dark and bright spin states. Remarkably, we find that strong dipole-dipole interactions stabilize the dark condensate. As a result, the dark phase persists up to densities high enough for a dark quantum liquid to form. The striking experimental observation of a step-like dependence of the exciton density on the pump power is reproduced quantitatively by a model describing the nonequilibrium dynamics of driven coupled dark and bright condensates. This unique behavior marks a dynamical condensation to dark states with lifetimes as long as a millisecond, followed by a brightening transition at high densities.
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16
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Xie M, MacDonald AH. Electrical Reservoirs for Bilayer Excitons. PHYSICAL REVIEW LETTERS 2018; 121:067702. [PMID: 30141649 DOI: 10.1103/physrevlett.121.067702] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Indexed: 06/08/2023]
Abstract
The ground state of two-dimensional (2D) electron systems with equal low densities of electrons and holes in nearby layers is an exciton fluid. We show that a reservoir for excitons can be established by contacting the two layers separately and maintaining the chemical potential difference at a value less than the spatially indirect band gap, thereby avoiding the presence of free carriers in either layer. Equilibration between the exciton fluid and the contacts proceeds via a process involving virtual intermediate states in which an unpaired electron or hole virtually occupies a free carrier state in one of the 2D layers. We derive an approximate relationship between the exciton-contact equilibration rate and the electrical conductances between the contacts and individual 2D layers when the contact chemical potentials align with the free-carrier bands, and explain how electrical measurements can be used to measure thermodynamic properties of the exciton fluids.
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Affiliation(s)
- Ming Xie
- Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA
| | - A H MacDonald
- Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA
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17
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Misra S, Stern M, Joshua A, Umansky V, Bar-Joseph I. Experimental Study of the Exciton Gas-Liquid Transition in Coupled Quantum Wells. PHYSICAL REVIEW LETTERS 2018; 120:047402. [PMID: 29437436 DOI: 10.1103/physrevlett.120.047402] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2017] [Indexed: 06/08/2023]
Abstract
We study the exciton gas-liquid transition in GaAs/AlGaAs coupled quantum wells. Below a critical temperature, T_{C}=4.8 K, and above a threshold laser power density the system undergoes a phase transition into a liquid state. We determine the density-temperature phase diagram over the temperature range 0.1-4.8 K. We find that the latent heat increases linearly with temperature at T≲1.1 K, similarly to a Bose-Einstein condensate transition, and becomes constant at 1.1≲T<4.8 K. Resonant Rayleigh scattering measurements reveal that the disorder in the sample is strongly suppressed and the diffusion coefficient sharply increases with decreasing temperature at T<T_{C}, allowing the liquid to spread over large distances away from the excitation region. We suggest that our findings are manifestations of a quantum liquid behavior.
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Affiliation(s)
- Subhradeep Misra
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Michael Stern
- Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Arjun Joshua
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Vladimir Umansky
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Israel Bar-Joseph
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
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18
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Combescot M, Combescot R, Dubin F. Bose-Einstein condensation and indirect excitons: a review. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2017; 80:066501. [PMID: 28355164 DOI: 10.1088/1361-6633/aa50e3] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We review recent progress on Bose-Einstein condensation (BEC) of semiconductor excitons. The first part deals with theory, the second part with experiments. This Review is written at a time where the problem of exciton Bose-Einstein condensation has just been revived by the understanding that the exciton condensate must be dark because the exciton ground state is not coupled to light. Here, we theoretically discuss this missed understanding before providing its experimental support through experiments that scrutinize indirect excitons made of spatially separated electrons and holes. The theoretical part first discusses condensation of elementary bosons. In particular, the necessary inhibition of condensate fragmentation by exchange interaction is stressed, before extending the discussion to interacting bosons with spin degrees of freedom. The theoretical part then considers composite bosons made of two fermions like semiconductor excitons. The spin structure of the excitons is detailed, with emphasis on the crucial fact that ground-state excitons are dark: indeed, this imposes the exciton Bose-Einstein condensate to be not coupled to light in the dilute regime. Condensate fragmentations are then reconsidered. In particular, it is shown that while at low density, the exciton condensate is fully dark, it acquires a bright component, coherent with the dark one, beyond a density threshold: in this regime, the exciton condensate is 'gray'. The experimental part first discusses optical creation of indirect excitons in quantum wells, and the detection of their photoluminescence. Exciton thermalisation is also addressed, as well as available approaches to estimate the exciton density. We then switch to specific experiments where indirect excitons form a macroscopic fragmented ring. We show that such ring provides efficient electrostatic trapping in the region of the fragments where an essentially-dark exciton Bose-Einstein condensate is formed at sub-Kelvin bath temperatures. The macroscopic spatial coherence of the photoluminescence observed in this essentially dark region confirms this conclusion.
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Affiliation(s)
- Monique Combescot
- Institut des NanoSciences de Paris, Université Pierre et Marie Curie, CNRS, Tour 22, 4 place Jussieu, 75005 Paris, France
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19
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20
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Cohen K, Shilo Y, West K, Pfeiffer L, Rapaport R. Dark High Density Dipolar Liquid of Excitons. NANO LETTERS 2016; 16:3726-3731. [PMID: 27183418 DOI: 10.1021/acs.nanolett.6b01061] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The possible phases and the nanoscale particle correlations of two-dimensional interacting dipolar particles is a long-sought problem in many-body physics. Here we observe a spontaneous condensation of trapped two-dimensional dipolar excitons with internal spin degrees of freedom from an interacting gas into a high density, closely packed liquid state made mostly of dark dipoles. Another phase transition, into a bright, highly repulsive plasma, is observed at even higher excitation powers. The dark liquid state is formed below a critical temperature Tc ≈ 4.8 K, and it is manifested by a clear spontaneous spatial condensation to a smaller and denser cloud, suggesting an attractive part to the interaction which goes beyond the purely repulsive dipole-dipole forces. Contributions from quantum mechanical fluctuations are expected to be significant in this strongly correlated, long living dark liquid. This is a new example of a two-dimensional atomic-like interacting dipolar liquid, but where the coupling of light to its internal spin degrees of freedom plays a crucial role in the dynamical formation and the nature of resulting condensed dark ground state.
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Affiliation(s)
- Kobi Cohen
- Racah Institute of Physics, The Hebrew University of Jerusalem , Jerusalem 9190401, Israel
| | - Yehiel Shilo
- Racah Institute of Physics, The Hebrew University of Jerusalem , Jerusalem 9190401, Israel
| | - Ken West
- Department of Electrical Engineering, Princeton University , Princeton, New Jersey 08544, United States
| | - Loren Pfeiffer
- Department of Electrical Engineering, Princeton University , Princeton, New Jersey 08544, United States
| | - Ronen Rapaport
- Racah Institute of Physics, The Hebrew University of Jerusalem , Jerusalem 9190401, Israel
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21
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Quereda J, San-Jose P, Parente V, Vaquero-Garzon L, Molina-Mendoza AJ, Agraït N, Rubio-Bollinger G, Guinea F, Roldán R, Castellanos-Gomez A. Strong Modulation of Optical Properties in Black Phosphorus through Strain-Engineered Rippling. NANO LETTERS 2016; 16:2931-7. [PMID: 27042865 DOI: 10.1021/acs.nanolett.5b04670] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Controlling the bandgap through local-strain engineering is an exciting avenue for tailoring optoelectronic materials. Two-dimensional crystals are particularly suited for this purpose because they can withstand unprecedented nonhomogeneous deformations before rupture; one can literally bend them and fold them up almost like a piece of paper. Here, we study multilayer black phosphorus sheets subjected to periodic stress to modulate their optoelectronic properties. We find a remarkable shift of the optical absorption band-edge of up to ∼0.7 eV between the regions under tensile and compressive stress, greatly exceeding the strain tunability reported for transition metal dichalcogenides. This observation is supported by theoretical models that also predict that this periodic stress modulation can yield to quantum confinement of carriers at low temperatures. The possibility of generating large strain-induced variations in the local density of charge carriers opens the door for a variety of applications including photovoltaics, quantum optics, and two-dimensional optoelectronic devices.
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Affiliation(s)
- Jorge Quereda
- Department de Física de la Materia Condensada, Universidad Autónoma de Madrid , 28049 Madrid, Spain
| | - Pablo San-Jose
- Instituto de Ciencia de Materiales de Madrid, CSIC , Sor Juana Ines de la Cruz 3, 28049 Madrid, Spain
| | - Vincenzo Parente
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia) , Campus de Cantoblanco, E-28049 Madrid, Spain
| | - Luis Vaquero-Garzon
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia) , Campus de Cantoblanco, E-28049 Madrid, Spain
| | - Aday J Molina-Mendoza
- Department de Física de la Materia Condensada, Universidad Autónoma de Madrid , 28049 Madrid, Spain
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia) , Campus de Cantoblanco, E-28049 Madrid, Spain
| | - Nicolás Agraït
- Department de Física de la Materia Condensada, Universidad Autónoma de Madrid , 28049 Madrid, Spain
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia) , Campus de Cantoblanco, E-28049 Madrid, Spain
- Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid , E-28049 Madrid, Spain
| | - Gabino Rubio-Bollinger
- Department de Física de la Materia Condensada, Universidad Autónoma de Madrid , 28049 Madrid, Spain
- Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid , E-28049 Madrid, Spain
| | - Francisco Guinea
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia) , Campus de Cantoblanco, E-28049 Madrid, Spain
| | - Rafael Roldán
- Instituto de Ciencia de Materiales de Madrid, CSIC , Sor Juana Ines de la Cruz 3, 28049 Madrid, Spain
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia) , Campus de Cantoblanco, E-28049 Madrid, Spain
| | - Andres Castellanos-Gomez
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia) , Campus de Cantoblanco, E-28049 Madrid, Spain
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22
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Berman OL, Kezerashvili RY, Kolmakov GV, Pomirchi LM. Spontaneous formation and nonequilibrium dynamics of a soliton-shaped Bose-Einstein condensate in a trap. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 91:062901. [PMID: 26172766 DOI: 10.1103/physreve.91.062901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Indexed: 06/04/2023]
Abstract
The Bose-stimulated self-organization of a quasi-two-dimensional nonequilibrium Bose-Einstein condensate in an in-plane potential is proposed. We obtained the solution of the nonlinear, driven-dissipative Gross-Pitaevskii equation for a Bose-Einstein condensate trapped in an external asymmetric parabolic potential within the method of the spectral expansion. We found that, in sharp contrast to previous observations, the condensate can spontaneously acquire a solitonlike shape for spatially homogeneous pumping. This condensate soliton performs oscillatory motion in a parabolic trap and, also, can spontaneously rotate. Stability of the condensate soliton in the spatially asymmetric trap is analyzed. In addition to the nonlinear dynamics of nonequilibrium Bose-Einstein condensates of ultracold atoms, our findings can be applied to the condensates of quantum well excitons and cavity polaritons in semiconductor heterostructure, and to the condensates of photons.
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Affiliation(s)
- Oleg L Berman
- Physics Department, New York City College of Technology, The City University of New York, Brooklyn, New York 11201, USA
| | - Roman Ya Kezerashvili
- Physics Department, New York City College of Technology, The City University of New York, Brooklyn, New York 11201, USA
| | - German V Kolmakov
- Physics Department, New York City College of Technology, The City University of New York, Brooklyn, New York 11201, USA
| | - Leonid M Pomirchi
- Physics Department, New York City College of Technology, The City University of New York, Brooklyn, New York 11201, USA
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23
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Combescot M, Combescot R, Alloing M, Dubin F. Effects of fermion exchange on the polarization of exciton condensates. PHYSICAL REVIEW LETTERS 2015; 114:090401. [PMID: 25793784 DOI: 10.1103/physrevlett.114.090401] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Indexed: 06/04/2023]
Abstract
Exchange interaction is responsible for the stability of elementary boson condensates with respect to momentum fragmentation. This remains true for composite bosons when single fermion exchanges are included but spin degrees of freedom are ignored. Here, we show that their inclusion can produce a spin fragmentation of the dark exciton condensate, i.e., an unpolarized condensate with an equal amount of spin (+2) and (-2) excitons not coupled to light. The composite boson many-body formalism allows us to predict that, for spatially indirect excitons, the condensate polarization switches from unpolarized to fully polarized when the distance between the layers confining electrons and holes increases. Importantly, the threshold distance for this switch lies in a regime fully accessible to experiments.
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Affiliation(s)
- Monique Combescot
- Institut des NanoSciences de Paris, Université Pierre et Marie Curie, CNRS, Tour 22, 4 Place Jussieu, 75005 Paris, France
| | - Roland Combescot
- Laboratoire de Physique Statistique, Ecole Normale Supérieure, UPMC Paris 06, Université Paris Diderot, CNRS, 24 Rue Lhomond, 75005 Paris, France
- Institut Universitaire de France, 103 Boulevard Saint-Michel, 75005 Paris, France
| | - Mathieu Alloing
- Institut des NanoSciences de Paris, Université Pierre et Marie Curie, CNRS, Tour 22, 4 Place Jussieu, 75005 Paris, France
- ICFO-The Institute of Photonic Sciences, 3 Avenidad Carl Friedrich Gauss, 08860 Castelldefels (Barcelona), Spain
| | - François Dubin
- Institut des NanoSciences de Paris, Université Pierre et Marie Curie, CNRS, Tour 22, 4 Place Jussieu, 75005 Paris, France
- ICFO-The Institute of Photonic Sciences, 3 Avenidad Carl Friedrich Gauss, 08860 Castelldefels (Barcelona), Spain
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24
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Kuznetsova YY, Andreakou P, Hasling MW, Leonard JR, Calman EV, Butov LV, Hanson M, Gossard AC. Two-dimensional snowflake trap for indirect excitons. OPTICS LETTERS 2015; 40:589-592. [PMID: 25680157 DOI: 10.1364/ol.40.000589] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We present experimental proof of principle for two-dimensional electrostatic traps for indirect excitons. A confining trap potential for indirect excitons is created by a snowflake-shaped electrode pattern. We demonstrate collection of indirect excitons from all directions to the trap center and control of the trap potential by voltage.
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25
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Abstract
Wave turbulence (WT) occurs in systems of strongly interacting nonlinear waves and can lead to energy flows across length and frequency scales much like those that are well known in vortex turbulence. Typically, the energy passes although a nondissipative inertial range until it reaches a small enough scale that viscosity becomes important and terminates the cascade by dissipating the energy as heat. Wave turbulence in quantum fluids is of particular interest, partly because revealing experiments can be performed on a laboratory scale, and partly because WT among the Kelvin waves on quantized vortices is believed to play a crucial role in the final stages of the decay of (vortex) quantum turbulence. In this short review, we provide a perspective on recent work on WT in quantum fluids, setting it in context and discussing the outlook for the next few years. We outline the theory, review briefly the experiments carried out to date using liquid H2 and liquid (4)He, and discuss some nonequilibrium excitonic superfluids in which WT has been predicted but not yet observed experimentally. By way of conclusion, we consider the medium- and longer-term outlook for the field.
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26
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Su JJ, Kim NY, Yamamoto Y, Macdonald AH. Ferminoic physics in dipolariton condensates. PHYSICAL REVIEW LETTERS 2014; 112:116401. [PMID: 24702391 DOI: 10.1103/physrevlett.112.116401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Indexed: 06/03/2023]
Abstract
An exciton polariton is an extremely light bosonic quasiparticle that is composed of an exciton and a photon. We report on a theoretical study of exciton-polariton condensation in a system with tunnel-coupled quantum wells. Because their excitons can carry an electric dipole moment, these systems have been referred to as dipolariton condensates. We use a fermionic mean-field theory that can address quantum well and other internal exciton degrees of freedom to describe the new physics present in dipolariton condensates. We find that the role of underlying fermonic degrees of freedom is enhanced and predict that metallic condensates can occur at high carrier densities.
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Affiliation(s)
- Jung-Jung Su
- National Institute of Informatics, 2-1-2 Hitotsubashi, Chiyoda-ku, Tokyo 101-8430, Japan and Edward L. Ginzton Laboratory, Stanford University, Stanford, California 94305-4085, USA and Department of Electrophysics, National Chiao Tung University, Hsinchu 300, Taiwan
| | - Na Young Kim
- Edward L. Ginzton Laboratory, Stanford University, Stanford, California 94305-4085, USA
| | - Yoshihisa Yamamoto
- National Institute of Informatics, 2-1-2 Hitotsubashi, Chiyoda-ku, Tokyo 101-8430, Japan and Edward L. Ginzton Laboratory, Stanford University, Stanford, California 94305-4085, USA
| | - Allan H Macdonald
- Department of Physics, University of Texas at Austin, Austin, Texas 78712, USA
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27
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Particle correlations and evidence for dark state condensation in a cold dipolar exciton fluid. Nat Commun 2013; 4:2335. [DOI: 10.1038/ncomms3335] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Accepted: 07/19/2013] [Indexed: 11/08/2022] Open
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Perali A, Neilson D, Hamilton AR. High-temperature superfluidity in double-bilayer graphene. PHYSICAL REVIEW LETTERS 2013; 110:146803. [PMID: 25167022 DOI: 10.1103/physrevlett.110.146803] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2012] [Indexed: 06/03/2023]
Abstract
Exciton bound states in solids between electrons and holes are predicted to form a superfluid at high temperatures. We show that by employing atomically thin crystals such as a pair of adjacent bilayer graphene sheets, equilibrium superfluidity of electron-hole pairs should be achievable for the first time. The transition temperatures are well above liquid helium temperatures. Because the sample parameters needed for the device have already been attained in similar graphene devices, our work suggests a new route toward realizing high-temperature superfluidity in existing quality graphene samples.
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Affiliation(s)
- A Perali
- Università di Camerino, 62032 Camerino, Italy
| | - D Neilson
- Università di Camerino, 62032 Camerino, Italy and NEST CNR-INFM, 56127 Pisa, Italy
| | - A R Hamilton
- School of Physics, University of New South Wales, 2052 Sydney, Australia
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Alloing M, Lemaître A, Galopin E, Dubin F. Optically programmable excitonic traps. Sci Rep 2013; 3:1578. [PMID: 23546532 PMCID: PMC3613794 DOI: 10.1038/srep01578] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2012] [Accepted: 03/13/2013] [Indexed: 11/23/2022] Open
Abstract
With atomic systems, optically programmed trapping potentials have led to remarkable progress in quantum optics and quantum information science. Programmable trapping potentials could have a similar impact on studies of semiconductor quasi-particles, particularly excitons. However, engineering such potentials inside a semiconductor heterostructure remains an outstanding challenge and optical techniques have not yet achieved a high degree of control. Here, we synthesize optically programmable trapping potentials for indirect excitons of bilayer heterostructures. Our approach relies on the injection and spatial patterning of charges trapped in a field-effect device. We thereby imprint in-situ and on-demand electrostatic traps into which we optically inject cold and dense ensembles of excitons. This technique creates new opportunities to improve state-of-the-art technologies for the study of collective quantum behavior of excitons and also for the functionalisation of emerging exciton-based opto-electronic circuits.
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Affiliation(s)
- Mathieu Alloing
- ICFO-The Institute of Photonic Sciences, Av. Carl Friedrich Gauss, num. 3, 08860 Castelldefels (Barcelona), Spain
| | - Aristide Lemaître
- Laboratoire de Photonique et Nanostructures, CNRS, Route de Nozay, 91460 Marcoussis, France
| | - Elisabeth Galopin
- Laboratoire de Photonique et Nanostructures, CNRS, Route de Nozay, 91460 Marcoussis, France
| | - François Dubin
- ICFO-The Institute of Photonic Sciences, Av. Carl Friedrich Gauss, num. 3, 08860 Castelldefels (Barcelona), Spain
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30
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Castellanos-Gomez A, Roldán R, Cappelluti E, Buscema M, Guinea F, van der Zant HSJ, Steele GA. Local strain engineering in atomically thin MoS2. NANO LETTERS 2013; 13:5361-6. [PMID: 24083520 DOI: 10.1021/nl402875m] [Citation(s) in RCA: 469] [Impact Index Per Article: 42.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Controlling the bandstructure through local-strain engineering is an exciting avenue for tailoring optoelectronic properties of materials at the nanoscale. Atomically thin materials are particularly well-suited for this purpose because they can withstand extreme nonhomogeneous deformations before rupture. Here, we study the effect of large localized strain in the electronic bandstructure of atomically thin MoS2. Using photoluminescence imaging, we observe a strain-induced reduction of the direct bandgap and funneling of photogenerated excitons toward regions of higher strain. To understand these results, we develop a nonuniform tight-binding model to calculate the electronic properties of MoS2 nanolayers with complex and realistic local strain geometries, finding good agreement with our experimental results.
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Affiliation(s)
- Andres Castellanos-Gomez
- Kavli Institute of Nanoscience, Delft University of Technology , Lorentzweg 1, 2628 CJ Delft, The Netherlands
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31
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Xu TF, Jing XL, Luo HG, Wu WC, Liu CS. Interplay between periodicity and nonlinearity of indirect excitons in coupled quantum wells. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:455301. [PMID: 23072970 DOI: 10.1088/0953-8984/24/45/455301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Inspired by a recent experiment of localization-delocalization transition (LDT) of indirect excitons in lateral electrostatic lattices (Remeika et al 2009 Phys. Rev. Lett. 102 186803), we theoretically investigate the interplay between periodic potential and nonlinear interactions of indirect excitons in coupled quantum wells. It is shown that the model involving both attractive two-body and repulsive three-body interactions can lead to a natural account for the LDT of excitons across the lattice when reducing lattice amplitude or increasing particle density. In addition, the observations that the smooth component of the photoluminescent energy increases with increasing exciton density and that the exciton interaction energy is close to the lattice amplitude at the transition are also qualitatively explained. Our model provides an alternative way of understanding the underlying physics of the exciton dynamics in lattice potential wells.
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Affiliation(s)
- T F Xu
- Department of Physics, Yanshan University, Qinhuangdao 066004, People's Republic of China
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32
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High AA, Leonard JR, Remeika M, Butov LV, Hanson M, Gossard AC. Reply to "comment on 'condensation of excitons in a trap'". NANO LETTERS 2012; 12:5422. [PMID: 22978516 DOI: 10.1021/nl302928v] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
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33
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Semkat D, Sobkowiak S, Manzke G, Stolz H. Comment on "condensation of excitons in a trap". NANO LETTERS 2012; 12:5055-5057. [PMID: 22822715 DOI: 10.1021/nl302504h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Affiliation(s)
- Dirk Semkat
- Institut für Physik, Universität Rostock, D-18051 Rostock, Germany
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