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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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Descamps T, Liu F, Hangleiter T, Kindel S, Kardynał BE, Bluhm H. Millikelvin confocal microscope with free-space access and high-frequency electrical control. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2024; 95:083706. [PMID: 39120446 DOI: 10.1063/5.0200889] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Accepted: 07/23/2024] [Indexed: 08/10/2024]
Abstract
Cryogenic confocal microscopy is a powerful method for studying solid state quantum devices such as single photon sources and optically controlled qubits. While the vast majority of such studies have been conducted at temperatures of a few Kelvin, experiments involving fragile quantum effects often require lower operating temperatures. To also allow for electrical dynamic control, microwave connectivity is required. For polarization-sensitive studies, free space optical access is advantageous compared to fiber coupling. Here we present a confocal microscope in a dilution refrigerator providing all the above features at temperatures below 100 mK. The installed high frequency cabling meets the requirements for state-of-the-art spin qubit experiments. As another unique advantage of our system, the sample fitting inside a large puck can be exchanged while keeping the cryostat cold with minimal realignment. Assessing the performance of the instrument, we demonstrate confocal imaging, sub-nanosecond modulation of the emission wavelength of a suitable sample, and an electron temperature of 76 mK. While the instrument was constructed primarily with the development of optical interfaces to electrically controlled qubits in mind, it can be used for many experiments involving quantum transport, solid state quantum optics, and microwave-optical transducers.
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Affiliation(s)
- Thomas Descamps
- JARA-FIT Institute Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, 52074 Aachen, Germany
| | - Feng Liu
- JARA-FIT Institute Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, 52074 Aachen, Germany
| | - Tobias Hangleiter
- JARA-FIT Institute Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, 52074 Aachen, Germany
| | - Sebastian Kindel
- JARA-FIT Institute Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, 52074 Aachen, Germany
| | - Beata E Kardynał
- Peter Grünberg Institute, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
- Department of Physics, RWTH Aachen University, 52074 Aachen, Germany
| | - Hendrik Bluhm
- JARA-FIT Institute Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, 52074 Aachen, Germany
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3
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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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4
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Sun X, Zhu Y, Qin H, Liu B, Tang Y, Lü T, Rahman S, Yildirim T, Lu Y. Enhanced interactions of interlayer excitons in free-standing heterobilayers. Nature 2022; 610:478-484. [PMID: 36224395 DOI: 10.1038/s41586-022-05193-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2021] [Accepted: 08/04/2022] [Indexed: 11/09/2022]
Abstract
Strong, long-range dipole-dipole interactions between interlayer excitons (IXs) can lead to new multiparticle correlation regimes1,2, which drive the system into distinct quantum and classical phases2-5, including dipolar liquids, crystals and superfluids. Both repulsive and attractive dipole-dipole interactions have been theoretically predicted between IXs in a semiconductor bilayer2,6-8, but only repulsive interactions have been reported experimentally so far3,9-16. This study investigated free-standing, twisted (51°, 53°, 45°) tungsten diselenide/tungsten disulfide (WSe2/WS2) heterobilayers, in which we observed a transition in the nature of dipolar interactions among IXs, from repulsive to attractive. This was caused by quantum-exchange-correlation effects, leading to the appearance of a robust interlayer biexciton phase (formed by two IXs), which has been theoretically predicted6-8 but never observed before in experiments. The reduced dielectric screening in a free-standing heterobilayer not only resulted in a much higher formation efficiency of IXs, but also led to strongly enhanced dipole-dipole interactions, which enabled us to observe the many-body correlations of pristine IXs at the two-dimensional quantum limit. In addition, we firstly observed several emission peaks from moiré-trapped IXs at room temperature in a well-aligned, free-standing WSe2/WS2 heterobilayer. Our findings open avenues for exploring new quantum phases with potential for applications in non-linear optics.
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Affiliation(s)
- Xueqian Sun
- School of Engineering, College of Engineering and Computer Science, the Australian National University, Canberra, Australian Capital Territory, Australia
| | - Yi Zhu
- School of Engineering, College of Engineering and Computer Science, the Australian National University, Canberra, Australian Capital Territory, Australia
| | - Hao Qin
- School of Engineering, College of Engineering and Computer Science, the Australian National University, Canberra, Australian Capital Territory, Australia
| | - Boqing Liu
- School of Engineering, College of Engineering and Computer Science, the Australian National University, Canberra, Australian Capital Territory, Australia
| | - Yilin Tang
- School of Engineering, College of Engineering and Computer Science, the Australian National University, Canberra, Australian Capital Territory, Australia
| | - Tieyu Lü
- Department of Physics and Institute of Theoretical Physics and Astrophysics, Xiamen University, Xiamen, China
| | - Sharidya Rahman
- School of Engineering, College of Engineering and Computer Science, the Australian National University, Canberra, Australian Capital Territory, Australia
| | - Tanju Yildirim
- Center for Functional Sensor and Actuator, Research Center for Functional Materials, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki, Japan
| | - Yuerui Lu
- School of Engineering, College of Engineering and Computer Science, the Australian National University, Canberra, Australian Capital Territory, Australia. .,Australian Research Council Centre of Excellence for Quantum Computation and Communication Technology, the Australian National University, Canberra, Australian Capital Territory, Australia.
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5
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Electrically tunable quantum confinement of neutral excitons. Nature 2022; 606:298-304. [PMID: 35614215 DOI: 10.1038/s41586-022-04634-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Accepted: 03/14/2022] [Indexed: 01/07/2023]
Abstract
Confining particles to distances below their de Broglie wavelength discretizes their motional state. This fundamental effect is observed in many physical systems, ranging from electrons confined in atoms or quantum dots1,2 to ultracold atoms trapped in optical tweezers3,4. In solid-state photonics, a long-standing goal has been to achieve fully tunable quantum confinement of optically active electron-hole pairs, known as excitons. To confine excitons, existing approaches mainly rely on material modulation5, which suffers from poor control over the energy and position of trapping potentials. This has severely impeded the engineering of large-scale quantum photonic systems. Here we demonstrate electrically controlled quantum confinement of neutral excitons in 2D semiconductors. By combining gate-defined in-plane electric fields with inherent interactions between excitons and free charges in a lateral p-i-n junction, we achieve exciton confinement below 10 nm. Quantization of excitonic motion manifests in the measured optical response as a ladder of discrete voltage-dependent states below the continuum. Furthermore, we observe that our confining potentials lead to a strong modification of the relative wave function of excitons. Our technique provides an experimental route towards creating scalable arrays of identical single-photon sources and has wide-ranging implications for realizing strongly correlated photonic phases6,7 and on-chip optical quantum information processors8,9.
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6
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Li W, Lu X, Dubey S, Devenica L, Srivastava A. Dipolar interactions between localized interlayer excitons in van der Waals heterostructures. NATURE MATERIALS 2020; 19:624-629. [PMID: 32284596 DOI: 10.1038/s41563-020-0661-4] [Citation(s) in RCA: 58] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Accepted: 03/10/2020] [Indexed: 05/22/2023]
Abstract
Although photons in free space barely interact, matter can mediate interactions between them resulting in optical nonlinearities. Such interactions at the single-quantum level result in an on-site photon repulsion, crucial for photon-based quantum information processing and for realizing strongly interacting many-body states of light. Here, we report repulsive dipole-dipole interactions between electric field-tuneable, localized interlayer excitons in the MoSe2/WSe2 heterobilayer. The presence of a single, localized exciton with an out-of-plane, non-oscillating dipole moment increases the energy of the second excitation by ~2 meV-an order of magnitude larger than the emission linewidth and corresponding to an inter-dipole distance of ~7 nm. At higher excitation power, multi-exciton complexes appear at systematically higher energies. The magnetic field dependence of the emission polarization is consistent with the spin-valley singlet nature of the dipolar molecular state. Our finding represents a step towards the creation of excitonic few- and many-body states such as dipolar crystals with spin-valley spinor in van der Waals heterostructures.
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Affiliation(s)
- Weijie Li
- Department of Physics, Emory University, Atlanta, GA, USA
| | - Xin Lu
- Department of Physics, Emory University, Atlanta, GA, USA
| | - Sudipta Dubey
- Department of Physics, Emory University, Atlanta, GA, USA
| | - Luka Devenica
- Department of Physics, Emory University, Atlanta, GA, 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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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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9
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Dang S, Anankine R, Gomez C, Lemaître A, Holzmann M, Dubin F. Defect Proliferation at the Quasicondensate Crossover of Two-Dimensional Dipolar Excitons Trapped in Coupled GaAs Quantum Wells. PHYSICAL REVIEW LETTERS 2019; 122:117402. [PMID: 30951355 DOI: 10.1103/physrevlett.122.117402] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Indexed: 06/09/2023]
Abstract
We study ultracold dipolar excitons confined in a 10 μm trap of a double GaAs quantum well. Based on the local density approximation, we unveil for the first time the equation of state of excitons. Specifically, in this regime and below a critical temperature of about 1 K, we show that for a local density n∼(2-3)×10^{10} cm^{-2} a coherent quasicondensate phase forms in the inner region of the trap, encircled by a more dilute and normal component in the outer rim. Remarkably, this spatial arrangement correlates directly with the concentration of defects in the exciton density, which is strongly decreased in the quasicondensed region, consistent with a superfluid phase. Thus, our observations point towards a Berezinskii-Kosterlitz-Thouless crossover for two-dimensional excitons.
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Affiliation(s)
- Suzanne Dang
- Institut des Nanosciences de Paris, CNRS and Sorbonne University, 4 pl. Jussieu, 75005 Paris, France
| | - Romain Anankine
- Institut des Nanosciences de Paris, CNRS and Sorbonne University, 4 pl. Jussieu, 75005 Paris, France
| | - Carmen Gomez
- Centre for Nanoscience and Nanotechnology-C2N, University Paris Saclay and CNRS, Route de Nozay, 91460 Marcoussis, France
| | - Aristide Lemaître
- Centre for Nanoscience and Nanotechnology-C2N, University Paris Saclay and CNRS, Route de Nozay, 91460 Marcoussis, France
| | - Markus Holzmann
- Université Grenoble Alpes, CNRS, LPMMC, 3800 Grenoble, France
| | - François Dubin
- Institut des Nanosciences de Paris, CNRS and Sorbonne University, 4 pl. Jussieu, 75005 Paris, France
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10
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Togan E, Lim HT, Faelt S, Wegscheider W, Imamoglu A. Enhanced Interactions between Dipolar Polaritons. PHYSICAL REVIEW LETTERS 2018; 121:227402. [PMID: 30547610 DOI: 10.1103/physrevlett.121.227402] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 10/16/2018] [Indexed: 06/09/2023]
Abstract
Nonperturbative coupling between cavity photons and excitons leads to the formation of hybrid light-matter excitations, termed polaritons. In structures where photon absorption leads to the creation of excitons with aligned permanent dipoles, the elementary excitations, termed dipolar polaritons, are expected to exhibit enhanced interactions. Here, we report a substantial increase in interaction strength between dipolar polaritons as the size of the dipole is increased by tuning the applied gate voltage. To this end, we use coupled quantum well structures embedded inside a microcavity where coherent electron tunneling between the wells creates the excitonic dipole. Modifications of the interaction strength are characterized by measuring the changes in the reflected light intensity when polaritons are driven with a resonant laser. The factor of 6.5 increase in the interaction-strength-to-linewidth ratio that we obtain indicates that dipolar polaritons could constitute an important step towards a demonstration of the polariton blockade effect, and thereby to form the building blocks of many-body states of light.
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Affiliation(s)
- Emre Togan
- Institute of Quantum Electronics, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Hyang-Tag Lim
- Institute of Quantum Electronics, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Stefan Faelt
- Institute of Quantum Electronics, ETH Zurich, CH-8093 Zurich, Switzerland
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | | | - Atac Imamoglu
- Institute of Quantum Electronics, ETH Zurich, CH-8093 Zurich, Switzerland
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11
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Rivera P, Yu H, Seyler KL, Wilson NP, Yao W, Xu X. Interlayer valley excitons in heterobilayers of transition metal dichalcogenides. NATURE NANOTECHNOLOGY 2018; 13:1004-1015. [PMID: 30104622 DOI: 10.1038/s41565-018-0193-0] [Citation(s) in RCA: 180] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Accepted: 06/11/2018] [Indexed: 05/12/2023]
Abstract
Stacking different two-dimensional crystals into van der Waals heterostructures provides an exciting approach to designing quantum materials that can harness and extend the already fascinating properties of the constituents. Heterobilayers of transition metal dichalcogenides are particularly attractive for low-dimensional semiconductor optics because they host interlayer excitons-with electrons and holes localized in different layers-which inherit valley-contrasting physics from the monolayers and thereby possess various novel and appealing properties compared to other solid-state nanostructures. This Review presents the contemporary experimental and theoretical understanding of these interlayer excitons. We discuss their unique optical properties arising from the underlying valley physics, the strong many-body interactions and electrical control resulting from the electric dipole moment, and the unique effects of a moiré superlattice on the interlayer exciton potential landscape and optical properties.
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Affiliation(s)
- Pasqual Rivera
- Department of Physics, University of Washington, Seattle, WA, USA
| | - Hongyi Yu
- Department of Physics and Center of Theoretical and Computational Physics, University of Hong Kong, Hong Kong, China
| | - Kyle L Seyler
- Department of Physics, University of Washington, Seattle, WA, USA
| | - Nathan P Wilson
- Department of Physics, University of Washington, Seattle, WA, USA
| | - Wang Yao
- Department of Physics and Center of Theoretical and Computational Physics, University of Hong Kong, Hong Kong, China.
| | - Xiaodong Xu
- Department of Physics, University of Washington, Seattle, WA, USA.
- Department of Materials Science and Engineering, University of Washington, Seattle, WA, USA.
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12
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Rosenberg I, Liran D, Mazuz-Harpaz Y, West K, Pfeiffer L, Rapaport R. Strongly interacting dipolar-polaritons. SCIENCE ADVANCES 2018; 4:eaat8880. [PMID: 30345358 PMCID: PMC6195342 DOI: 10.1126/sciadv.aat8880] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Accepted: 09/10/2018] [Indexed: 05/14/2023]
Abstract
Exciton-polaritons are mutually interacting quantum hybridizations of confined photons and electronic excitations. Here, we demonstrate a system of optically guided, electrically polarized exciton-polaritons ("dipolaritons") that displays up to 200-fold enhancement of the polariton-polariton interaction strength compared to unpolarized polaritons. The magnitude of the dipolar interaction enhancement can be turned on and off and can be easily tuned over a very wide range by varying the applied polarizing electric field. The large interaction strengths and the very long propagation distances of these fully guided dipolaritons open up new opportunities for realizing complex quantum circuitry and quantum simulators, as well as topological states based on exciton-polaritons, for which the interactions between polaritons need to be large and spatially or temporally controlled. The results also raise fundamental questions on the origin of these large enhancements.
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Affiliation(s)
- Itamar Rosenberg
- Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Dror Liran
- Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Yotam Mazuz-Harpaz
- Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Kenneth West
- Department of Electrical Engineering, Princeton University, Princeton, NJ 08544, USA
| | - Loren Pfeiffer
- Department of Electrical Engineering, Princeton University, Princeton, NJ 08544, USA
| | - Ronen Rapaport
- Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
- Applied Physics Department, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
- Corresponding author.
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13
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Roch JG, Leisgang N, Froehlicher G, Makk P, Watanabe K, Taniguchi T, Schönenberger C, Warburton RJ. Quantum-Confined Stark Effect in a MoS 2 Monolayer van der Waals Heterostructure. NANO LETTERS 2018; 18:1070-1074. [PMID: 29378141 DOI: 10.1021/acs.nanolett.7b04553] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The optics of dangling-bond-free van der Waals heterostructures containing transition metal dichalcogenides are dominated by excitons. A crucial property of a confined exciton is the quantum confined Stark effect (QCSE). Here, such a heterostructure is used to probe the QCSE by applying a uniform vertical electric field across a molybdenum disulfide (MoS2) monolayer. The photoluminescence emission energies of the neutral and charged excitons shift quadratically with the applied electric field, provided that the electron density remains constant, demonstrating that the exciton can be polarized. Stark shifts corresponding to about half the homogeneous linewidth were achieved. Neutral and charged exciton polarizabilities of (7.8 ± 1.0) × 10-10 and (6.4 ± 0.9) × 10-10 D m V-1 at relatively low electron density (∼1012 cm-2) have been extracted, respectively. These values are one order of magnitude lower than the previously reported values but in line with theoretical calculations. The methodology presented here is versatile and can be applied to other semiconducting layered materials.
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Affiliation(s)
- Jonas G Roch
- Department of Physics, University of Basel , Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Nadine Leisgang
- Department of Physics, University of Basel , Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Guillaume Froehlicher
- Department of Physics, University of Basel , Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Peter Makk
- Department of Physics, University of Basel , Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Kenji Watanabe
- National Institute for Material Science , 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- National Institute for Material Science , 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Christian Schönenberger
- Department of Physics, University of Basel , Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Richard J Warburton
- Department of Physics, University of Basel , Klingelbergstrasse 82, CH-4056 Basel, Switzerland
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Miller B, Steinhoff A, Pano B, Klein J, Jahnke F, Holleitner A, Wurstbauer U. Long-Lived Direct and Indirect Interlayer Excitons in van der Waals Heterostructures. NANO LETTERS 2017; 17:5229-5237. [PMID: 28742367 DOI: 10.1021/acs.nanolett.7b01304] [Citation(s) in RCA: 132] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
We report the observation of a doublet structure in the low-temperature photoluminescence of interlayer excitons in heterostructures consisting of monolayer MoSe2 and WSe2. Both peaks exhibit long photoluminescence lifetimes of several tens of nanoseconds up to 100 ns verifying the interlayer nature of the excitons. The energy and line width of both peaks show unusual temperature and power dependences. While the low-energy peak dominates the spectra at low power and low temperatures, the high-energy peak dominates for high power and temperature. We explain the findings by two kinds of interlayer excitons being either indirect or quasi-direct in reciprocal space. Our results provide fundamental insights into long-lived interlayer states in van der Waals heterostructures with possible bosonic many-body interactions.
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Affiliation(s)
- Bastian Miller
- Walter Schottky Institut and Physics-Department, Technical University of Munich , Am Coulombwall 4a, 85748 Garching, Germany
- Nanosystems Initiative Munich (NIM) , Schellingstrasse 4, 80799 München, Germany
| | - Alexander Steinhoff
- Institut für Theoretische Physik, Universität Bremen , P.O. Box 330 440, 28334 Bremen, Germany
| | - Borja Pano
- Walter Schottky Institut and Physics-Department, Technical University of Munich , Am Coulombwall 4a, 85748 Garching, Germany
| | - Julian Klein
- Walter Schottky Institut and Physics-Department, Technical University of Munich , Am Coulombwall 4a, 85748 Garching, Germany
- Nanosystems Initiative Munich (NIM) , Schellingstrasse 4, 80799 München, Germany
| | - Frank Jahnke
- Institut für Theoretische Physik, Universität Bremen , P.O. Box 330 440, 28334 Bremen, Germany
| | - Alexander Holleitner
- Walter Schottky Institut and Physics-Department, Technical University of Munich , Am Coulombwall 4a, 85748 Garching, Germany
- Nanosystems Initiative Munich (NIM) , Schellingstrasse 4, 80799 München, Germany
| | - Ursula Wurstbauer
- Walter Schottky Institut and Physics-Department, Technical University of Munich , Am Coulombwall 4a, 85748 Garching, Germany
- Nanosystems Initiative Munich (NIM) , Schellingstrasse 4, 80799 München, Germany
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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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Anankine R, Beian M, Dang S, Alloing M, Cambril E, Merghem K, Carbonell CG, Lemaître A, Dubin F. Quantized Vortices and Four-Component Superfluidity of Semiconductor Excitons. PHYSICAL REVIEW LETTERS 2017; 118:127402. [PMID: 28388190 DOI: 10.1103/physrevlett.118.127402] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Indexed: 06/07/2023]
Abstract
We study spatially indirect excitons of GaAs quantum wells, confined in a 10 μm electrostatic trap. Below a critical temperature of about 1 K, we detect macroscopic spatial coherence and quantized vortices in the weak photoluminescence emitted from the trap. These quantum signatures are restricted to a narrow range of density, in a dilute regime. They manifest the formation of a four-component superfluid, made by a low population of optically bright excitons coherently coupled to a dominant fraction of optically dark excitons.
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Affiliation(s)
- Romain Anankine
- Sorbonne Universités, UPMC Univ. Paris 06, CNRS-UMR 7588, Institut des NanoSciences de Paris, 4 Place Jussieu, F-75005 Paris, France
| | - Mussie Beian
- Sorbonne Universités, UPMC Univ. Paris 06, CNRS-UMR 7588, Institut des NanoSciences de Paris, 4 Place Jussieu, F-75005 Paris, France
- ICFO-The Institute of Photonic Sciences, Av. Carl Friedrich Gauss, num. 3, 08860 Castelldefels, Spain
| | - Suzanne Dang
- Sorbonne Universités, UPMC Univ. Paris 06, CNRS-UMR 7588, Institut des NanoSciences de Paris, 4 Place Jussieu, F-75005 Paris, France
| | - Mathieu Alloing
- Sorbonne Universités, UPMC Univ. Paris 06, CNRS-UMR 7588, Institut des NanoSciences de Paris, 4 Place Jussieu, F-75005 Paris, France
| | - Edmond Cambril
- Laboratoire de Photonique et Nanostructures, LPN/CNRS, Route de Nozay, 91460 Marcoussis, France
| | - Kamel Merghem
- Laboratoire de Photonique et Nanostructures, LPN/CNRS, Route de Nozay, 91460 Marcoussis, France
| | - Carmen Gomez Carbonell
- Laboratoire de Photonique et Nanostructures, LPN/CNRS, Route de Nozay, 91460 Marcoussis, France
| | - Aristide Lemaître
- Laboratoire de Photonique et Nanostructures, LPN/CNRS, Route de Nozay, 91460 Marcoussis, France
| | - François Dubin
- Sorbonne Universités, UPMC Univ. Paris 06, CNRS-UMR 7588, Institut des NanoSciences de Paris, 4 Place Jussieu, F-75005 Paris, France
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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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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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Grasselli F, Bertoni A, Goldoni G. Space- and time-dependent quantum dynamics of spatially indirect excitons in semiconductor heterostructures. J Chem Phys 2015; 142:034701. [PMID: 25612719 DOI: 10.1063/1.4905483] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We study the unitary propagation of a two-particle one-dimensional Schrödinger equation by means of the Split-Step Fourier method, to study the coherent evolution of a spatially indirect exciton (IX) in semiconductor heterostructures. The mutual Coulomb interaction of the electron-hole pair and the electrostatic potentials generated by external gates and acting on the two particles separately are taken into account exactly in the two-particle dynamics. As relevant examples, step/downhill and barrier/well potential profiles are considered. The space- and time-dependent evolutions during the scattering event as well as the asymptotic time behavior are analyzed. For typical parameters of GaAs-based devices, the transmission or reflection of the pair turns out to be a complex two-particle process, due to comparable and competing Coulomb, electrostatic, and kinetic energy scales. Depending on the intensity and anisotropy of the scattering potentials, the quantum evolution may result in excitation of the IX internal degrees of freedom, dissociation of the pair, or transmission in small periodic IX wavepackets due to dwelling of one particle in the barrier region. We discuss the occurrence of each process in the full parameter space of the scattering potentials and the relevance of our results for current excitronic technologies.
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Affiliation(s)
- Federico Grasselli
- Department of Physics, Informatics and Mathematics, University of Modena and Reggio Emilia, Modena, Italy
| | - Andrea Bertoni
- CNR-NANO S3, Institute for Nanoscience, Via Campi 213/a, 41125 Modena, Italy
| | - Guido Goldoni
- Department of Physics, Informatics and Mathematics, University of Modena and Reggio Emilia, Modena, Italy
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Affiliation(s)
- Michael Stern
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Vladimir Umansky
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Israel Bar-Joseph
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
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