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Zhang L, Gu L, Ni R, Xie M, Park S, Jang H, Ma R, Taniguchi T, Watanabe K, Zhou Y. Electrical Control and Transport of Tightly Bound Interlayer Excitons in a MoSe_{2}/hBN/MoSe_{2} Heterostructure. PHYSICAL REVIEW LETTERS 2024; 132:216903. [PMID: 38856288 DOI: 10.1103/physrevlett.132.216903] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Revised: 03/11/2024] [Accepted: 04/15/2024] [Indexed: 06/11/2024]
Abstract
Controlling interlayer excitons in Van der Waals heterostructures holds promise for exploring Bose-Einstein condensates and developing novel optoelectronic applications, such as excitonic integrated circuits. Despite intensive studies, several key fundamental properties of interlayer excitons, such as their binding energies and interactions with charges, remain not well understood. Here we report the formation of momentum-direct interlayer excitons in a high-quality MoSe_{2}/hBN/MoSe_{2} heterostructure under an electric field, characterized by bright photoluminescence (PL) emission with high quantum yield and a narrow linewidth of less than 4 meV. These interlayer excitons show electrically tunable emission energy spanning ∼180 meV through the Stark effect, and exhibit a sizable binding energy of ∼81 meV in the intrinsic regime, along with trion binding energies of a few millielectronvolts. Remarkably, we demonstrate the long-range transport of interlayer excitons with a characteristic diffusion length exceeding 10 μm, which can be attributed, in part, to their dipolar repulsive interactions. Spatially and polarization-resolved spectroscopic studies reveal rich exciton physics in the system, such as valley polarization, local trapping, and the possible existence of dark interlayer excitons. The formation and transport of tightly bound interlayer excitons with narrow linewidth, coupled with the ability to electrically manipulate their properties, open exciting new avenues for exploring quantum many-body physics, including excitonic condensate and superfluidity, and for developing novel optoelectronic devices, such as exciton and photon routers.
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Affiliation(s)
- Lifu Zhang
- Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA
| | - Liuxin Gu
- Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA
| | - Ruihao Ni
- Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA
| | - Ming Xie
- Condensed Matter Theory Center, University of Maryland, College Park, Maryland 20742, USA
| | - Suji Park
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Houk Jang
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Rundong Ma
- Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA
| | - Takashi Taniguchi
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - You Zhou
- Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA
- Maryland Quantum Materials Center, College Park, Maryland 20742, USA
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2
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Sethi G, Cuma M, Liu F. Excitonic Condensate in Flat Valence and Conduction Bands of Opposite Chirality. PHYSICAL REVIEW LETTERS 2023; 130:186401. [PMID: 37204894 DOI: 10.1103/physrevlett.130.186401] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2022] [Revised: 07/01/2022] [Accepted: 04/14/2023] [Indexed: 05/21/2023]
Abstract
Excitonic Bose-Einstein condensation (EBEC) has drawn increasing attention recently with the emergence of 2D materials. A general criterion for EBEC, as expected in an excitonic insulator (EI) state, is to have negative exciton formation energies in a semiconductor. Here, using exact diagonalization of a multiexciton Hamiltonian modeled in a diatomic kagome lattice, we demonstrate that the negative exciton formation energies are only a prerequisite but insufficient condition for realizing an EI. By a comparative study between the cases of both conduction and valence flat bands (FBs) versus that of a parabolic conduction band, we further show that the presence and increased FB contribution to exciton formation provide an attractive avenue to stabilize the excitonic condensate, as confirmed by calculations and analyses of multiexciton energies, wave functions, and reduced density matrices. Our results warrant a similar many-exciton analysis for other known and/or new candidates of EIs and demonstrate the FBs of opposite parity as a unique platform for studying exciton physics, paving the way to material realization of spinor BEC and spin superfluidity.
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Affiliation(s)
- Gurjyot Sethi
- Department of Materials Science and Engineering, University of Utah, Salt Lake City, Utah 84112, USA
| | - Martin Cuma
- Center for High Performance Computing, University of Utah, Salt Lake City, Utah 84112, USA
| | - Feng Liu
- Department of Materials Science and Engineering, University of Utah, Salt Lake City, Utah 84112, USA
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3
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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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4
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Stability of Spin-Wave Solitons in Bose-Einstein Condensates of Magnons: A Possible Application in Ferromagnetic Films. MATERIALS 2022; 15:ma15072551. [PMID: 35407882 PMCID: PMC8999475 DOI: 10.3390/ma15072551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Revised: 03/20/2022] [Accepted: 03/23/2022] [Indexed: 11/28/2022]
Abstract
In this paper, we theoretically investigate the stability of spin-wave solitons in Bose-Einstein condensates of repulsive magnons, confined by an inhomogeneous external magnetic field described by a Gaussian well. For this purpose, we use the quasi-one-dimensional Gross-Pitaevskii equation to describe the behavior of the condensate. In order to solve the Gross-Pitaevskii equation, we used two different approaches: one analytical (variational method) and another numerical (split-step Crank-Nicolson method). The stability of the solutions and the validation of the numerical results were confirmed, respectively, through the anti-VK criterion and the virial theorem. Furthermore, the simulations described the behavior of physical quantities of interest such as chemical potential, energy per magnon and central density as a function of the nonlinearity of the model (magnon-magnon interactions). The theoretical results provide subsidies for a better understanding of the nonlinear phenomena related to the Bose-Einstein condensates of magnons in ferromagnetic films.
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5
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Moiré pattern of interference dislocations in condensate of indirect excitons. Nat Commun 2021; 12:1175. [PMID: 33608546 PMCID: PMC7895953 DOI: 10.1038/s41467-021-21353-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Accepted: 01/15/2021] [Indexed: 11/08/2022] Open
Abstract
Interference patterns provide direct measurement of coherent propagation of matter waves in quantum systems. Superfluidity in Bose-Einstein condensates of excitons can enable long-range ballistic exciton propagation and can lead to emerging long-scale interference patterns. Indirect excitons (IXs) are formed by electrons and holes in separated layers. The theory predicts that the reduced IX recombination enables IX superfluid propagation over macroscopic distances. Here, we present dislocation-like phase singularities in interference patterns produced by condensate of IXs. We analyze how exciton vortices and skyrmions should appear in the interference experiments and show that the observed interference dislocations are not associated with these phase defects. We show that the observed interference dislocations originate from the moiré effect in combined interference patterns of propagating condensate matter waves. The interference dislocations are formed by the IX matter waves ballistically propagating over macroscopic distances. The long-range ballistic IX propagation is the evidence for IX condensate superfluidity.
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Pan D, Fu Y, Spitha N, Zhao Y, Roy CR, Morrow DJ, Kohler DD, Wright JC, Jin S. Deterministic fabrication of arbitrary vertical heterostructures of two-dimensional Ruddlesden-Popper halide perovskites. NATURE NANOTECHNOLOGY 2021; 16:159-165. [PMID: 33257896 DOI: 10.1038/s41565-020-00802-2] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Accepted: 10/20/2020] [Indexed: 05/24/2023]
Abstract
Ruddlesden-Popper lead halide perovskites have emerged as a new class of two-dimensional semiconductors with tunable optoelectronic properties, potentially offering unlimited heterostructure configurations for exploration. However, the practical realization of such heterostructures is challenging because of the difficulty in achieving controllable direct synthesis or van der Waals integration of halide perovskites due to their mobile and fragile crystal lattices. Here we report direct growth of large-area nanosheets of diverse phase-pure Ruddlesden-Popper perovskites with thicknesses down to one monolayer at the solution-air interface and a reliable approach for gently transferring and stacking these nanosheets. These advances enable the deterministic fabrication of arbitrary vertical heterostructures and multi-heterostructures of Ruddlesden-Popper perovskites with greater structural degrees of freedom that define the electronic structures of the heterojunctions. Such rationally designed heterostructures exhibit interesting interlayer properties, such as interlayer carrier transfer and reduction of the photoluminescence linewidth, and could enable the exploration of exciton physics and optoelectronic applications.
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Affiliation(s)
- Dongxu Pan
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Yongping Fu
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA.
| | - Natalia Spitha
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Yuzhou Zhao
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Chris R Roy
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Darien J Morrow
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Daniel D Kohler
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - John C Wright
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA.
| | - Song Jin
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA.
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7
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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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8
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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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9
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Esteve-Paredes JJ, Pakdel S, Palacios JJ. Quenching of Exciton Recombination in Strained Two-Dimensional Monochalcogenides. PHYSICAL REVIEW LETTERS 2019; 123:077402. [PMID: 31491087 DOI: 10.1103/physrevlett.123.077402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Indexed: 06/10/2023]
Abstract
We predict that long-lived excitons with very large binding energies can also exist in a single or few layers of monochalcogenides such as GaSe. Our theoretical study shows that excitons confined by a radial local strain field are unable to recombine despite electrons and holes coexisting in space. The localized single-particle states are calculated in the envelope function approximation based on a three-band k·p Hamiltonian obtained from density-functional-theory calculations. The binding energy and the decay rate of the exciton ground state are computed after including correlations in the basis of electron-hole pairs. The interplay between the localized strain and the caldera-type valence band characteristic of few-layered monochalcogenides creates localized electron and hole states with very different quantum numbers which hinders the recombination even for singlet excitons.
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Affiliation(s)
- J J Esteve-Paredes
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
| | - Sahar Pakdel
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
- Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C, Denmark
- School of Electrical and Computer Engineering, University College of Engineering, University of Tehran, Tehran 14395-515, Iran
| | - J J Palacios
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
- Instituto Nicolás Cabrera (INC) and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, E-28049 Madrid, Spain
- Department of Physics, University of Texas, Austin, Texas 78712, USA
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10
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Bozhko DA, Kreil AJE, Musiienko-Shmarova HY, Serga AA, Pomyalov A, L'vov VS, Hillebrands B. Bogoliubov waves and distant transport of magnon condensate at room temperature. Nat Commun 2019; 10:2460. [PMID: 31165731 PMCID: PMC6549249 DOI: 10.1038/s41467-019-10118-y] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Accepted: 04/12/2019] [Indexed: 11/08/2022] Open
Abstract
A macroscopic collective motion of a Bose-Einstein condensate (BEC) is commonly associated with phenomena such as superconductivity and superfluidity, often generalised by the term supercurrent. Another type of motion of a quantum condensate is second sound-a wave of condensate's parameters. Recently, we reported on the decay of a BEC of magnons caused by a supercurrent outflow of the BEC from the locally heated area of a room temperature magnetic film. Here, we present the observation of a macroscopic BEC transport mechanism related to the excitation of second sound. The condensed magnons, being propelled out of the heated area, form compact humps of BEC density, which propagate many hundreds of micrometers in the form of distinct second sound-Bogoliubov waves. This discovery advances the physics of quasiparticles and allows for the application of related transport phenomena for low-loss data transfer in magnon spintronics devices.
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Affiliation(s)
- Dmytro A Bozhko
- Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663, Kaiserslautern, Germany
| | - Alexander J E Kreil
- Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663, Kaiserslautern, Germany
| | - Halyna Yu Musiienko-Shmarova
- Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663, Kaiserslautern, Germany
| | - Alexander A Serga
- Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663, Kaiserslautern, Germany
| | - Anna Pomyalov
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Victor S L'vov
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Burkard Hillebrands
- Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663, Kaiserslautern, Germany.
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11
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Kreil AJE, Bozhko DA, Musiienko-Shmarova HY, Vasyuchka VI, L'vov VS, Pomyalov A, Hillebrands B, Serga AA. From Kinetic Instability to Bose-Einstein Condensation and Magnon Supercurrents. PHYSICAL REVIEW LETTERS 2018; 121:077203. [PMID: 30169064 DOI: 10.1103/physrevlett.121.077203] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Indexed: 06/08/2023]
Abstract
Evolution of an overpopulated gas of magnons to a Bose-Einstein condensate and excitation of a magnon supercurrent, propelled by a phase gradient in the condensate wave function, can be observed at room temperature by means of the Brillouin light scattering spectroscopy in an yttrium iron garnet material. We study these phenomena in a wide range of external magnetic fields in order to understand their properties when externally pumped magnons are transferred towards the condensed state via two distinct channels: a multistage Kolmogorov-Zakharov cascade of the weak-wave turbulence or a one-step kinetic instability process. Our main result is that opening the kinetic instability channel leads to the formation of a much denser magnon condensate and to a stronger magnon supercurrent compared to the cascade mechanism alone.
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Affiliation(s)
- Alexander J E Kreil
- Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany
| | - Dmytro A Bozhko
- Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany
| | - Halyna Yu Musiienko-Shmarova
- Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany
| | - Vitaliy I Vasyuchka
- Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany
| | - Victor S L'vov
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Anna Pomyalov
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Burkard Hillebrands
- Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany
| | - Alexander A Serga
- Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany
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12
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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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13
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Autti S, Dmitriev VV, Mäkinen JT, Rysti J, Soldatov AA, Volovik GE, Yudin AN, Eltsov VB. Bose-Einstein Condensation of Magnons and Spin Superfluidity in the Polar Phase of ^{3}He. PHYSICAL REVIEW LETTERS 2018; 121:025303. [PMID: 30085748 DOI: 10.1103/physrevlett.121.025303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 02/09/2018] [Indexed: 06/08/2023]
Abstract
The polar phase of ^{3}He, which is topological spin-triplet superfluid with the Dirac nodal line in the spectrum of Bogoliubov quasiparticles, has been recently stabilized in a nanoconfined geometry. We pump magnetic excitations (magnons) into the sample of polar phase and observe how they form a Bose-Einstein condensate, revealed by coherent precession of the magnetization of the sample. Spin superfluidity, which supports this coherence, is associated with the spontaneous breaking of U(1) symmetry by the phase of precession. We observe the corresponding Nambu-Goldstone boson and measure its mass emerging when applied rf field violates the U(1) symmetry explicitly. We suggest that the magnon BEC in the polar phase is a powerful probe for topological objects such as vortices and solitons and topological nodes in the fermionic spectrum.
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Affiliation(s)
- S Autti
- Department of Applied Physics, Aalto University, P.O. Box 15100, FI-00076 AALTO, Finland
| | - V V Dmitriev
- P. L. Kapitza Institute for Physical Problems of RAS, 119334 Moscow, Russia
| | - J T Mäkinen
- Department of Applied Physics, Aalto University, P.O. Box 15100, FI-00076 AALTO, Finland
| | - J Rysti
- Department of Applied Physics, Aalto University, P.O. Box 15100, FI-00076 AALTO, Finland
| | - A A Soldatov
- P. L. Kapitza Institute for Physical Problems of RAS, 119334 Moscow, Russia
- Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Russia
| | - G E Volovik
- Department of Applied Physics, Aalto University, P.O. Box 15100, FI-00076 AALTO, Finland
- Landau Institute for Theoretical Physics, 142432 Chernogolovka, Russia
| | - A N Yudin
- P. L. Kapitza Institute for Physical Problems of RAS, 119334 Moscow, Russia
| | - V B Eltsov
- Department of Applied Physics, Aalto University, P.O. Box 15100, FI-00076 AALTO, Finland
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14
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Pancharatnam-Berry phase in condensate of indirect excitons. Nat Commun 2018; 9:2158. [PMID: 29867086 PMCID: PMC5986757 DOI: 10.1038/s41467-018-04667-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Accepted: 05/03/2018] [Indexed: 11/08/2022] Open
Abstract
The Pancharatnam-Berry phase is a geometric phase acquired over a cycle of parameters in the Hamiltonian governing the evolution of the system. Here, we report on the observation of the Pancharatnam-Berry phase in a condensate of indirect excitons (IXs) in a GaAs-coupled quantum well structure. The Pancharatnam-Berry phase is directly measured by detecting phase shifts of interference fringes in IX interference patterns. Correlations are found between the phase shifts, polarization pattern of IX emission, and onset of IX spontaneous coherence. The evolving Pancharatnam-Berry phase is acquired due to coherent spin precession in IX condensate and is observed with no decay over lengths exceeding 10 μm indicating long-range coherent spin transport.
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15
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Calman EV, Fogler MM, Butov LV, Hu S, Mishchenko A, Geim AK. Indirect excitons in van der Waals heterostructures at room temperature. Nat Commun 2018; 9:1895. [PMID: 29760404 PMCID: PMC5951911 DOI: 10.1038/s41467-018-04293-7] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Accepted: 04/13/2018] [Indexed: 12/24/2022] Open
Abstract
Indirect excitons (IXs) are explored both for studying quantum Bose gases in semiconductor materials and for the development of excitonic devices. IXs were extensively studied in III-V and II-VI semiconductor heterostructures where IX range of existence has been limited to low temperatures. Here, we present the observation of IXs at room temperature in van der Waals transition metal dichalcogenide (TMD) heterostructures. This is achieved in TMD heterostructures based on monolayers of MoS2 separated by atomically thin hexagonal boron nitride. The IXs we realize in the TMD heterostructure have lifetimes orders of magnitude longer than lifetimes of direct excitons in single-layer TMD and their energy is gate controlled. The realization of IXs at room temperature establishes the TMD heterostructures as a material platform both for a field of high-temperature quantum Bose gases of IXs and for a field of high-temperature excitonic devices.
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Affiliation(s)
- E V Calman
- Department of Physics, University of California at San Diego, 9500 Gillman Drive, La Jolla, CA, 92093-0319, USA.
| | - M M Fogler
- Department of Physics, University of California at San Diego, 9500 Gillman Drive, La Jolla, CA, 92093-0319, USA
| | - L V Butov
- Department of Physics, University of California at San Diego, 9500 Gillman Drive, La Jolla, CA, 92093-0319, USA
| | - S Hu
- School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
| | - A Mishchenko
- School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
| | - A K Geim
- School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
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16
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Manca M, Glazov MM, Robert C, Cadiz F, Taniguchi T, Watanabe K, Courtade E, Amand T, Renucci P, Marie X, Wang G, Urbaszek B. Enabling valley selective exciton scattering in monolayer WSe 2 through upconversion. Nat Commun 2017; 8:14927. [PMID: 28367962 PMCID: PMC5382264 DOI: 10.1038/ncomms14927] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Accepted: 02/14/2017] [Indexed: 12/14/2022] Open
Abstract
Excitons, Coulomb bound electron–hole pairs, are composite bosons and their interactions in traditional semiconductors lead to condensation and light amplification. The much stronger Coulomb interaction in transition metal dichalcogenides such as WSe2 monolayers combined with the presence of the valley degree of freedom is expected to provide new opportunities for controlling excitonic effects. But so far the bosonic character of exciton scattering processes remains largely unexplored in these two-dimensional materials. Here we show that scattering between B-excitons and A-excitons preferably happens within the same valley in momentum space. This leads to power dependent, negative polarization of the hot B-exciton emission. We use a selective upconversion technique for efficient generation of B-excitons in the presence of resonantly excited A-excitons at lower energy; we also observe the excited A-excitons state 2s. Detuning of the continuous wave, low-power laser excitation outside the A-exciton resonance (with a full width at half maximum of 4 meV) results in vanishing upconversion signal. Monolayer transition metal dichalcogenides host excitons, bound electron-hole pairs that play a pivotal role in optoelectronic applications relying on strong light-matter interaction. Here, the authors unveil the spectroscopic signature of boson scattering of two-dimensional excitons in monolayer WSe2.
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Affiliation(s)
- M Manca
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Av. Rangueil, Toulouse 31077, France
| | - M M Glazov
- Ioffe Institute, St Petersburg 194021, Russia
| | - C Robert
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Av. Rangueil, Toulouse 31077, France
| | - F Cadiz
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Av. Rangueil, Toulouse 31077, France
| | - T Taniguchi
- National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan
| | - K Watanabe
- National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan
| | - E Courtade
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Av. Rangueil, Toulouse 31077, France
| | - T Amand
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Av. Rangueil, Toulouse 31077, France
| | - P Renucci
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Av. Rangueil, Toulouse 31077, France
| | - X Marie
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Av. Rangueil, Toulouse 31077, France
| | - G Wang
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Av. Rangueil, Toulouse 31077, France
| | - B Urbaszek
- Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Av. Rangueil, Toulouse 31077, France
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17
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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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18
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Abstract
In this review paper we address one of the most rapidly developing new domains of semiconductor optics: light-matter coupling in semiconductor microcavities. Using the non-local dielectric response theory and transfer matrix technique, we show how two-dimensional confinement of a photonic mode coupled to an exciton resonance results in the appearance of two branches of exciton-polaritons, quasi-particles combining properties of photons and excitons. We obtain the dispersion relations of polaritons in microcavities and derive a condition for strong-weak coupling threshold. We show that being bosons, exciton-polaritons are subject to Bose-condensation which might result in emission of a coherent and monochromatic light in the strong coupling regime. A source of such coherent light is referred to as a polariton laser. We show that polariton lasers have theoretically no threshold and require essentially new basic physics as compared to conventional lasers described by Einstein theory. We give examples of model polariton laser structures expected to work at room temperature and overview the main difficulties on the way to producing these new opto-electronic devices.
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19
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Serga AA, Tiberkevich VS, Sandweg CW, Vasyuchka VI, Bozhko DA, Chumak AV, Neumann T, Obry B, Melkov GA, Slavin AN, Hillebrands B. Bose–Einstein condensation in an ultra-hot gas of pumped magnons. Nat Commun 2014; 5:3452. [DOI: 10.1038/ncomms4452] [Citation(s) in RCA: 87] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Accepted: 02/14/2014] [Indexed: 11/09/2022] Open
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20
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Kyriienko O, Kavokin AV, Shelykh IA. Superradiant terahertz emission by dipolaritons. PHYSICAL REVIEW LETTERS 2013; 111:176401. [PMID: 24206504 DOI: 10.1103/physrevlett.111.176401] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2012] [Revised: 06/17/2013] [Indexed: 06/02/2023]
Abstract
Dipolaritons are mixed light-matter quasiparticles formed in double quantum wells embedded in microcavities. Because of resonant coupling between direct and indirect excitons via electronic tunneling, dipolaritons possess large dipole moments. Resonant excitation of the cavity mode by a short pulse of light induces oscillations of the indirect exciton density with a characteristic frequency of Rabi flopping. This results in oscillations of a classical Hertz dipole array which generate supperradiant emission on a terahertz (THz) frequency. The resulting THz signal may be enhanced using the supplementary THz cavity in the weak coupling regime.
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Affiliation(s)
- O Kyriienko
- Science Institute, University of Iceland, Dunhagi-3, IS-107 Reykjavik, Iceland and Division of Physics and Applied Physics, Nanyang Technological University, 637371 Singapore
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21
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Vishnevsky DV, Flayac H, Nalitov AV, Solnyshkov DD, Gippius NA, Malpuech G. Skyrmion formation and optical spin-Hall effect in an expanding coherent cloud of indirect excitons. PHYSICAL REVIEW LETTERS 2013; 110:246404. [PMID: 25165945 DOI: 10.1103/physrevlett.110.246404] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Indexed: 06/03/2023]
Abstract
We provide a theoretical description of the polarization pattern and phase singularities experimentally evidenced recently in a condensate of indirect excitons [H. High et al., Nature 483, 584 (2012)]. We show that the averaging of the electron and hole orbital motion leads to a comparable spin-orbit interaction for both types of carriers. We demonstrate that the interplay between a radial coherent flux of bright indirect excitons and the Dresselhaus spin-orbit interaction results in the formation of spin domains and of topological defects similar to Skyrmions. We reproduce qualitatively all the features of the experimental data and obtain a polarization pattern as in the optical spin-Hall effect despite the different symmetry of the spin-orbit interactions.
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Affiliation(s)
- D V Vishnevsky
- Institut Pascal, PHOTON-N2, Clermont Université, Blaise Pascal University, CNRS, 24 avenue des Landais, 63177 Aubière Cedex, France
| | - H Flayac
- Institut Pascal, PHOTON-N2, Clermont Université, Blaise Pascal University, CNRS, 24 avenue des Landais, 63177 Aubière Cedex, France
| | - A V Nalitov
- Institut Pascal, PHOTON-N2, Clermont Université, Blaise Pascal University, CNRS, 24 avenue des Landais, 63177 Aubière Cedex, France
| | - D D Solnyshkov
- Institut Pascal, PHOTON-N2, Clermont Université, Blaise Pascal University, CNRS, 24 avenue des Landais, 63177 Aubière Cedex, France
| | - N A Gippius
- Institut Pascal, PHOTON-N2, Clermont Université, Blaise Pascal University, CNRS, 24 avenue des Landais, 63177 Aubière Cedex, France and A. M. Prokhorov General Physics Institute, RAS, Vavilova Street 38, Moscow 119991, Russia
| | - G Malpuech
- Institut Pascal, PHOTON-N2, Clermont Université, Blaise Pascal University, CNRS, 24 avenue des Landais, 63177 Aubière Cedex, France
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22
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Li F, Saslow WM, Pokrovsky VL. Phase diagram for magnon condensate in Yttrium Iron Garnet film. Sci Rep 2013; 3:1372. [PMID: 23455849 PMCID: PMC3586816 DOI: 10.1038/srep01372] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Accepted: 02/15/2013] [Indexed: 11/09/2022] Open
Abstract
Recently, magnons, which are quasiparticles describing the collective motion of spins, were found to undergo Bose-Einstein condensation (BEC) at room temperature in films of Yttrium Iron Garnet (YIG). Unlike other quasiparticle BEC systems, this system has a spectrum with two degenerate minima, which makes it possible for the system to have two condensates in momentum space. Recent Brillouin Light Scattering studies for a microwave-pumped YIG film of thickness d = 5 μm and field H = 1 kOe find a low-contrast interference pattern at the characteristic wavevector Q of the magnon energy minimum. In this report, we show that this modulation pattern can be quantitatively explained as due to unequal but coherent Bose-Einstein condensation of magnons into the two energy minima. Our theory predicts a transition from a high-contrast symmetric state to a low-contrast non-symmetric state on varying the d and H, and a new type of collective oscillation.
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Affiliation(s)
- Fuxiang Li
- Dept. of Physics, Texas A&M University, College Station, TX 77843-4242
| | - Wayne M. Saslow
- Dept. of Physics, Texas A&M University, College Station, TX 77843-4242
| | - Valery L. Pokrovsky
- Dept. of Physics, Texas A&M University, College Station, TX 77843-4242
- Landau Institute for Theoretical Physics, Chernogolovka, Moscow District 142432, Russia
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23
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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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24
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Nowik-Boltyk P, Dzyapko O, Demidov VE, Berloff NG, Demokritov SO. Spatially non-uniform ground state and quantized vortices in a two-component Bose-Einstein condensate of magnons. Sci Rep 2012; 2:482. [PMID: 22761990 PMCID: PMC3386517 DOI: 10.1038/srep00482] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Accepted: 06/13/2012] [Indexed: 11/08/2022] Open
Abstract
A gas of magnons in magnetic films differs from all other known systems demonstrating Bose-Einstein condensation (BEC), since it possesses two energetically degenerate lowest-energy quantum states with non-zero wave vectors ±k(BEC). Therefore, BEC in this system results in a spontaneously formed two-component Bose-Einstein condensate described by a linear combination of two spatially non-uniform wave-functions ∝exp(±ik(BEC)z), while condensates found in other physical systems are characterized by spatially uniform wave-functions. Here we report a study of BEC of magnons with sub-micrometer spatial resolution. We experimentally confirm the existence of the two wave-functions and show that their interference results in a non-uniform ground state of the condensate with the density oscillating in space. Additionally, we observe stable topological defects in the condensate. By comparing the experimental results with predictions of a theoretical model based on the Ginzburg-Landau equation, we identify these defects as quantized vortices.
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Affiliation(s)
- P. Nowik-Boltyk
- Institute for Applied Physics and Center for Nonlinear Science, University of Muenster, Corrensstr. 2-4, 48149 Muenster, Germany
| | - O. Dzyapko
- Institute for Applied Physics and Center for Nonlinear Science, University of Muenster, Corrensstr. 2-4, 48149 Muenster, Germany
| | - V. E. Demidov
- Institute for Applied Physics and Center for Nonlinear Science, University of Muenster, Corrensstr. 2-4, 48149 Muenster, Germany
| | - N. G. Berloff
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge, CB3 WA0, United Kingdom
| | - S. O. Demokritov
- Institute for Applied Physics and Center for Nonlinear Science, University of Muenster, Corrensstr. 2-4, 48149 Muenster, Germany
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25
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High AA, Leonard JR, Remeika M, Butov LV, Hanson M, Gossard AC. Condensation of excitons in a trap. NANO LETTERS 2012; 12:2605-2609. [PMID: 22509898 DOI: 10.1021/nl300983n] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Condensation is observed in a gas of indirect excitons confined in an electrostatic trap. Imaging and interferometric measurements detect that excitons condense at the trap bottom and exciton spontaneous coherence emerges with lowering temperature. Below a temperature of about 1 K, the direct signature of Bose-Einstein condensation, the extension of coherence over the entire cloud, is observed.
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Affiliation(s)
- A A High
- Department of Physics, University of California at San Diego, La Jolla, California 92093-0319, USA.
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26
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High AA, Leonard JR, Hammack AT, Fogler MM, Butov LV, Kavokin AV, Campman KL, Gossard AC. Spontaneous coherence in a cold exciton gas. Nature 2012; 483:584-8. [DOI: 10.1038/nature10903] [Citation(s) in RCA: 231] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Accepted: 01/17/2012] [Indexed: 11/09/2022]
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27
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Ali Can M, Hakioğlu T. Unconventional pairing in excitonic condensates under spin-orbit coupling. PHYSICAL REVIEW LETTERS 2009; 103:086404. [PMID: 19792744 DOI: 10.1103/physrevlett.103.086404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2008] [Revised: 07/22/2009] [Indexed: 05/28/2023]
Abstract
It is shown that Rashba and Dresselhaus spin-orbit couplings enhance the conclusive power in the experiments on the excitonic condensate by at least three low temperature effects. First, spin-orbit coupling facilitates the photoluminescence measurements via enhancing the bright contribution in the otherwise dominantly dark ground state. The second is the presence of a low temperature power law dependence of the specific heat and weakening of the second order transition at the critical temperature. The third is the appearance of the nondiagonal elements in the static spin susceptibility.
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Affiliation(s)
- M Ali Can
- Department of Physics, Bilkent University, 06800 Ankara, Turkey
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28
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McKemmish LK, Reimers JR, McKenzie RH, Mark AE, Hush NS. Penrose-Hameroff orchestrated objective-reduction proposal for human consciousness is not biologically feasible. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2009; 80:021912. [PMID: 19792156 DOI: 10.1103/physreve.80.021912] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2008] [Revised: 05/29/2009] [Indexed: 05/28/2023]
Abstract
Penrose and Hameroff have argued that the conventional models of a brain function based on neural networks alone cannot account for human consciousness, claiming that quantum-computation elements are also required. Specifically, in their Orchestrated Objective Reduction (Orch OR) model [R. Penrose and S. R. Hameroff, J. Conscious. Stud. 2, 99 (1995)], it is postulated that microtubules act as quantum processing units, with individual tubulin dimers forming the computational elements. This model requires that the tubulin is able to switch between alternative conformational states in a coherent manner, and that this process be rapid on the physiological time scale. Here, the biological feasibility of the Orch OR proposal is examined in light of recent experimental studies on microtubule assembly and dynamics. It is shown that the tubulins do not possess essential properties required for the Orch OR proposal, as originally proposed, to hold. Further, we consider also recent progress in the understanding of the long-lived coherent motions in biological systems, a feature critical to Orch OR, and show that no reformation of the proposal based on known physical paradigms could lead to quantum computing within microtubules. Hence, the Orch OR model is not a feasible explanation of the origin of consciousness.
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Affiliation(s)
- Laura K McKemmish
- School of Chemistry, The University of Sydney, New South Wales 2006, Australia
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29
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Fil DV, Shevchenko SI. Josephson vortex motion as a source for dissipation of superflow of e-h pairs in bilayers. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:215701. [PMID: 21825558 DOI: 10.1088/0953-8984/21/21/215701] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
It is shown that in a bilayer excitonic superconductor dissipative losses emerge under transmission of the current from the source to the load. These losses are proportional to the square of the interlayer tunneling amplitude and are independent of the value of the input current. The case of a quantum Hall bilayer is considered. The bilayer may work as a transmission line if the input current exceeds a certain critical value. An input current higher than the critical one induces Josephson vortices in the bilayer. The difference in electrochemical potentials is required to feed the load and it forces Josephson vortices to move. The state becomes non-stationary which leads to dissipation.
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Affiliation(s)
- D V Fil
- Institute for Single Crystals, National Academy of Science of Ukraine, Lenin Avenue 60, Kharkov 61001, Ukraine
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30
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Remeika M, Graves JC, Hammack AT, Meyertholen AD, Fogler MM, Butov LV, Hanson M, Gossard AC. Localization-delocalization transition of indirect excitons in lateral electrostatic lattices. PHYSICAL REVIEW LETTERS 2009; 102:186803. [PMID: 19518898 DOI: 10.1103/physrevlett.102.186803] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2009] [Indexed: 05/27/2023]
Abstract
We study transport of indirect excitons in GaAs/AlGaAs coupled quantum wells in linear lattices created by laterally modulated gate voltage. The localization-delocalization transition for transport across the lattice was observed with reducing lattice amplitude or increasing exciton density. The exciton interaction energy at the transition is close to the lattice amplitude. These results are consistent with the model, which attributes the localization-delocalization transition to the interaction-induced percolation of the exciton gas through the external potential. We also discuss applications of the lattice potentials for estimating the strength of disorder and exciton interaction.
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Affiliation(s)
- M Remeika
- Department of Physics, University of California at San Diego, La Jolla, California 92093-0319, USA
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31
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Chumak AV, Melkov GA, Demidov VE, Dzyapko O, Safonov VL, Demokritov SO. Bose-Einstein condensation of magnons under incoherent pumping. PHYSICAL REVIEW LETTERS 2009; 102:187205. [PMID: 19518909 DOI: 10.1103/physrevlett.102.187205] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2008] [Indexed: 05/27/2023]
Abstract
Bose-Einstein condensation in a gas of magnons pumped by an incoherent pumping source is experimentally studied at room temperature. We demonstrate that the condensation can be achieved in a gas of bosons under conditions of incoherent pumping. The critical transition point is shown to be almost independent of the frequency spectrum of the pumping source and is solely determined by the density of magnons. The electromagnetic power radiated by the magnon condensate is found to scale quadratically with the pumping power. The obtained results are in a good agreement with the theory of Bose-Einstein condensation of quasiequilibrium magnons.
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Affiliation(s)
- A V Chumak
- Department of Radiophysics, National Taras Schevchenko University of Kiev, 01033 Kiev, Ukraine.
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32
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High AA, Hammack AT, Butov LV, Mouchliadis L, Ivanov AL, Hanson M, Gossard AC. Indirect excitons in elevated traps. NANO LETTERS 2009; 9:2094-2098. [PMID: 19382780 DOI: 10.1021/nl900605b] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We report on the study of indirect excitons in elevated traps. The transition from a normal to elevated trap results in the appearance of narrow lines in the emission spectrum. The density, temperature, and voltage dependences indicate that these lines correspond to the emission of individual states of indirect excitons in a disorder potential in the elevated trap.
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Affiliation(s)
- A A High
- Department of Physics, University of California at San Diego, La Jolla, California 92093-0319, USA.
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33
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Butov LV. Cold exciton gases in coupled quantum well structures. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2007; 19:295202. [PMID: 21483054 DOI: 10.1088/0953-8984/19/29/295202] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Cold exciton gases can be implemented in coupled quantum well structures. In this contribution, we review briefly the recent works on spontaneous coherence of cold excitons and on trapping of cold excitons with laser light.
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Affiliation(s)
- L V Butov
- Department of Physics, University of California at San Diego, La Jolla, CA 92093-0319, USA
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34
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Hakioğlu T, Sahin M. Excitonic condensation under spin-orbit coupling and BEC-BCS crossover. PHYSICAL REVIEW LETTERS 2007; 98:166405. [PMID: 17501441 DOI: 10.1103/physrevlett.98.166405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2006] [Indexed: 05/15/2023]
Abstract
The condensation of electron-hole pairs is studied at zero temperature and in the presence of a weak spin-orbit coupling (SOC) in coupled quantum wells. Under realistic conditions, a perturbative SOC can have observable effects in the order parameter of the condensate. First, the fermion exchange symmetry is absent. As a result, the condensate spin has no definite parity. Additionally, the excitonic SOC breaks the rotational symmetry yielding a complex order parameter in an unconventional way; i.e., the phase pattern of the order parameter is a function of the condensate density. This is manifested through finite off-diagonal components of the static spin susceptibility, suggesting a new experimental method to confirm an excitonic condensate.
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Affiliation(s)
- T Hakioğlu
- Department of Physics and National Nanotechnology Research Center, Bilkent University, 06800 Ankara, Turkey
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35
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Yang S, Hammack AT, Fogler MM, Butov LV, Gossard AC. Coherence length of cold exciton gases in coupled quantum wells. PHYSICAL REVIEW LETTERS 2006; 97:187402. [PMID: 17155574 DOI: 10.1103/physrevlett.97.187402] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2006] [Indexed: 05/12/2023]
Abstract
A Mach-Zehnder interferometer with spatial and spectral resolution was used to probe spontaneous coherence in cold exciton gases, which are implemented experimentally in the ring of indirect excitons in coupled quantum wells. A strong enhancement of the exciton coherence length is observed at temperatures below a few Kelvin. The increase of the coherence length is correlated with the macroscopic spatial ordering of excitons. The coherence length at the lowest temperature corresponds to a very narrow spread of the exciton momentum distribution, much smaller than that for a classical exciton gas.
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Affiliation(s)
- Sen Yang
- Department of Physics, University of California at San Diego, La Jolla, California 92093-0319, USA
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36
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Deng H, Press D, Götzinger S, Solomon GS, Hey R, Ploog KH, Yamamoto Y. Quantum degenerate exciton-polaritons in thermal equilibrium. PHYSICAL REVIEW LETTERS 2006; 97:146402. [PMID: 17155273 DOI: 10.1103/physrevlett.97.146402] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2006] [Indexed: 05/12/2023]
Abstract
We study the momentum distribution and relaxation dynamics of semiconductor microcavity polaritons by angle-resolved and time-resolved spectroscopy. Above a critical pump level, the thermalization time of polaritons at positive detunings becomes shorter than their lifetime, and the polaritons form a quantum degenerate Bose-Einstein distribution in thermal equilibrium with the lattice.
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Affiliation(s)
- Hui Deng
- Quantum Entanglement Project, SORST, JST, Edward L. Ginzton Laboratory, Stanford University, Stanford, California 94305, USA
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37
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Balzer K, Nölle C, Bonitz M, Filinov A. Energy spectrum of strongly correlated electrons and indirect excitons in quantum dots. ACTA ACUST UNITED AC 2006. [DOI: 10.1002/pssc.200668104] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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38
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Filinov A, Bonitz M, Ludwig P, Lozovik YE. Path integral Monte Carlo results for Bose condensation of mesoscopic indirect excitons. ACTA ACUST UNITED AC 2006. [DOI: 10.1002/pssc.200668038] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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39
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Levitov LS, Simons BD, Butov LV. Pattern formation as a signature of quantum degeneracy in a cold exciton system. PHYSICAL REVIEW LETTERS 2005; 94:176404. [PMID: 15904321 DOI: 10.1103/physrevlett.94.176404] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2004] [Revised: 01/14/2005] [Indexed: 05/02/2023]
Abstract
The development of a Turing instability to a spatially modulated state in a photoexcited electron-hole system is proposed as a novel signature of exciton Bose statistics. We show that such an instability, driven by kinetics of exciton formation, can result from stimulated processes that build up near quantum degeneracy. The stability of an electron-hole interface which describes recently observed exciton rings is analyzed. Interface instability occurs below a critical temperature, with a periodic 1D pattern developing via a continuous (type II) transition, in a qualitative agreement with observations.
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Affiliation(s)
- L S Levitov
- Department of Physics, Center for Materials Sciences & Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
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40
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Keeling J, Levitov LS, Littlewood PB. Angular distribution of photoluminescence as a probe of bose condensation of trapped excitons. PHYSICAL REVIEW LETTERS 2004; 92:176402. [PMID: 15169175 DOI: 10.1103/physrevlett.92.176402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2003] [Indexed: 05/24/2023]
Abstract
Recent experiments on two-dimensional exciton systems have shown that excitons collect in shallow in-plane traps. We find that Bose condensation in a trap results in a dramatic change of the exciton photoluminescence (PL) angular distribution. The long-range coherence of the condensed state gives rise to a sharply focused peak of radiation in the direction normal to the plane. By comparing the PL profile with and without Bose condensation, we provide a simple diagnostic for the existence of a Bose condensate. The PL peak has strong temperature dependence due to the thermal order parameter phase fluctuations across the system. The angular PL distribution can also be used for imaging vortices in the trapped condensate. Vortex phase spatial variation leads to destructive interference of PL radiation in certain directions, creating nodes in the PL distribution that imprint the vortex configuration.
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Affiliation(s)
- Jonathan Keeling
- Cavendish Laboratory, Madingley Road, Cambridge CB3 OHE, United Kingdom
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41
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Butov LV, Levitov LS, Mintsev AV, Simons BD, Gossard AC, Chemla DS. Formation mechanism and low-temperature instability of exciton rings. PHYSICAL REVIEW LETTERS 2004; 92:117404. [PMID: 15089167 DOI: 10.1103/physrevlett.92.117404] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2003] [Indexed: 05/24/2023]
Abstract
The macroscopic rings observed in the photoluminescence patterns of excitons in coupled quantum wells are explained by a mechanism of carrier imbalance, transport, and recombination. The rings originate from the spatial separation of p and n carriers, and occur at the interface of the p and n domains, where excitons are generated. We explore the states of excitons in the ring over a range of temperatures down to 380 mK and report a transition of the ring into a periodic array of aggregates, a new low-temperature ordered exciton state.
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Affiliation(s)
- L V Butov
- Materials Sciences Division, E. O. Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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42
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Abstract
In the past decade, there has been an increasing number of experiments on spontaneous Bose coherence of excitons and polaritons. Four major areas of research are reviewed here: three-dimensional excitons in the bulk semiconductor Cu2O, two-dimensional excitons in coupled quantum wells, Coulomb drag experiments in coupled two-dimensional electron gases, and polaritons in semiconductor microcavities. The unifying theory of all these experiments is the effect of spontaneous symmetry breaking in the Bose-Einstein condensation phase transition.
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Affiliation(s)
- David Snoke
- Department of Physics, University of Pittsburgh, 3941 O'Hara Street, Pittsburgh, PA 15260, USA
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Abstract
There is a rich variety of quantum liquids -- such as superconductors, liquid helium and atom Bose-Einstein condensates -- that exhibit macroscopic coherence in the form of ordered arrays of vortices. Experimental observation of a macroscopically ordered electronic state in semiconductors has, however, remained a challenging and relatively unexplored problem. A promising approach for the realization of such a state is to use excitons, bound pairs of electrons and holes that can form in semiconductor systems. At low densities, excitons are Bose-particles, and at low temperatures, of the order of a few kelvin, excitons can form a quantum liquid -- that is, a statistically degenerate Bose gas or even a Bose-Einstein condensate. Here we report photoluminescence measurements of a quasi-two-dimensional exciton gas in GaAs/AlGaAs coupled quantum wells and the observation of a macroscopically ordered exciton state. Our spatially resolved measurements reveal fragmentation of the ring-shaped emission pattern into circular structures that form periodic arrays over lengths up to 1 mm.
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Affiliation(s)
- L V Butov
- Materials Sciences Division, E. O. Lawrence Berkeley National Laboratory, University of California, 94720, USA.
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44
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Kavokin A, Zamfirescu M, Gil B, Malpuech G. ZnO as a Material Mostly Adapted for Realisation of Room-Temperature Polariton Lasers. ACTA ACUST UNITED AC 2002. [DOI: 10.1002/1521-396x(200207)192:1<212::aid-pssa212>3.0.co;2-b] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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45
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46
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Butov LV, Lai CW, Ivanov AL, Gossard AC, Chemla DS. Towards Bose-Einstein condensation of excitons in potential traps. Nature 2002; 417:47-52. [PMID: 11986661 DOI: 10.1038/417047a] [Citation(s) in RCA: 104] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
An exciton is an electron-hole bound pair in a semiconductor. In the low-density limit, it is a composite Bose quasi-particle, akin to the hydrogen atom. Just as in dilute atomic gases, reducing the temperature or increasing the exciton density increases the occupation numbers of the low-energy states leading to quantum degeneracy and eventually to Bose-Einstein condensation (BEC). Because the exciton mass is small--even smaller than the free electron mass--exciton BEC should occur at temperatures of about 1 K, many orders of magnitude higher than for atoms. However, it is in practice difficult to reach BEC conditions, as the temperature of excitons can considerably exceed that of the semiconductor lattice. The search for exciton BEC has concentrated on long-lived excitons: the exciton lifetime against electron-hole recombination therefore should exceed the characteristic timescale for the cooling of initially hot photo-generated excitons. Until now, all experiments on atom condensation were performed on atomic gases confined in the potential traps. Inspired by these experiments, and using specially designed semiconductor nanostructures, we have collected quasi-two-dimensional excitons in an in-plane potential trap. Our photoluminescence measurements show that the quasi-two-dimensional excitons indeed condense at the bottom of the traps, giving rise to a statistically degenerate Bose gas.
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Affiliation(s)
- L V Butov
- Materials Sciences Division, E. O. Lawrence Berkeley National Laboratory, University of California at Berkeley, Berkeley, California 94720, USA.
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47
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Olaya-Castro A, Rodríguez FJ, Quiroga L, Tejedor C. Restrictions on the coherence of the ultrafast optical emission from an electron-hole-pair condensate. PHYSICAL REVIEW LETTERS 2001; 87:246403. [PMID: 11736522 DOI: 10.1103/physrevlett.87.246403] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2001] [Indexed: 05/23/2023]
Abstract
We report on the transfer of coherence from a quantum-well electron-hole condensate to the light it emits. As a function of density, the coherence of the electron-hole-pair system evolves from being full for the low-density Bose-Einstein condensate to a chaotic behavior for a high-density BCS-like state. This degree of coherence is transferred to the light emitted in a damped oscillatory way in the ultrafast regime. Additionally, the photon field exhibits squeezing properties during the transfer time. Our results suggest a new type of ultrafast experiments for detecting electron-hole-pair condensation.
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Affiliation(s)
- A Olaya-Castro
- Departamento de Física, Universidad de Los Andes, A.A. 4976, Bogotá D.C., Colombia
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48
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Butov LV, Lai CW, Chemla DS, Lozovik YE, Campman KL, Gossard AC. Observation of magnetically induced effective-mass enhancement of quasi-2D excitons. PHYSICAL REVIEW LETTERS 2001; 87:216804. [PMID: 11736364 DOI: 10.1103/physrevlett.87.216804] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2001] [Indexed: 05/23/2023]
Abstract
We present the first measurements of the dispersion relation of a quasi-2D magnetoexciton. We demonstrate that the magnetoexciton effective mass is determined by the coupling between the center-of-mass motion and internal structure and becomes overwhelmingly larger than the sum of the electron and hole masses in high magnetic fields.
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Affiliation(s)
- L V Butov
- Materials Sciences Division, E. O. Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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