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Wilson NP, Yao W, Shan J, Xu X. Excitons and emergent quantum phenomena in stacked 2D semiconductors. Nature 2021; 599:383-392. [PMID: 34789905 DOI: 10.1038/s41586-021-03979-1] [Citation(s) in RCA: 68] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Accepted: 09/01/2021] [Indexed: 11/09/2022]
Abstract
The design and control of material interfaces is a foundational approach to realize technologically useful effects and engineer material properties. This is especially true for two-dimensional (2D) materials, where van der Waals stacking allows disparate materials to be freely stacked together to form highly customizable interfaces. This has underpinned a recent wave of discoveries based on excitons in stacked double layers of transition metal dichalcogenides (TMDs), the archetypal family of 2D semiconductors. In such double-layer structures, the elegant interplay of charge, spin and moiré superlattice structure with many-body effects gives rise to diverse excitonic phenomena and correlated physics. Here we review some of the recent discoveries that highlight the versatility of TMD double layers to explore quantum optics and many-body effects. We identify outstanding challenges in the field and present a roadmap for unlocking the full potential of excitonic physics in TMD double layers and beyond, such as incorporating newly discovered ferroelectric and magnetic materials to engineer symmetries and add a new level of control to these remarkable engineered materials.
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Affiliation(s)
- Nathan P Wilson
- Department of Physics, University of Washington, Seattle, WA, USA.,Walter Schottky Institute, Technical University of Munich, Garching, Germany.,Munich Centre for Quantum Science and Technology, Munich, Germany
| | - Wang Yao
- Department of Physics, University of Hong Kong, Hong Kong, China.,HKU-UCAS Joint Institute of Theoretical and Computational Physics at Hong Kong, Hong Kong, China
| | - Jie Shan
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
| | - 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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2
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Klinovaja J, Stano P, Loss D. Topological Floquet Phases in Driven Coupled Rashba Nanowires. PHYSICAL REVIEW LETTERS 2016; 116:176401. [PMID: 27176529 DOI: 10.1103/physrevlett.116.176401] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Indexed: 06/05/2023]
Abstract
We consider periodically driven arrays of weakly coupled wires with conduction and valence bands of Rashba type and study the resulting Floquet states. This nonequilibrium system can be tuned into nontrivial phases such as topological insulators, Weyl semimetals, and dispersionless zero-energy edge mode regimes. In the presence of strong electron-electron interactions, we generalize these regimes to the fractional case, where elementary excitations have fractional charges e/m with m being an odd integer.
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Affiliation(s)
- Jelena Klinovaja
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Peter Stano
- RIKEN Center for Emergent Matter Science, Wako, Saitama 351-0198, Japan
- Institute of Physics, Slovak Academy of Sciences, 845 11 Bratislava, Slovakia
| | - Daniel Loss
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
- RIKEN Center for Emergent Matter Science, Wako, Saitama 351-0198, Japan
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3
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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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Ye J, Shi T, Jiang L. Angle-resolved photoluminescence spectrum of the exciton condensate in electron-hole semiconductor bilayers. PHYSICAL REVIEW LETTERS 2009; 103:177401. [PMID: 19905781 DOI: 10.1103/physrevlett.103.177401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2009] [Indexed: 05/28/2023]
Abstract
The electron-hole semiconductor bilayer system is one of the most promising systems to search for exciton superfluid. The exciton superfluid is metastable and will eventually decay through emitting photons. Here we show that the angle-resolved photon spectrum, momentum distribution curve, energy distribution curve, and quasiparticle excitation spectrum in the exciton superfluid show many unique and unusual features not shared by any other atomic or condensed matter systems. Observing all these salient features in the photoluminescence experiments can provide convincing evidence for exciton superfluid in electron-hole semiconductor bilayers. We also comment on relevant experimental data in both exciton and exciton-polariton systems and also suggest possible future experiments to test our theoretical predictions.
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Affiliation(s)
- Jinwu Ye
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
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Stern M, Garmider V, Umansky V, Bar-Joseph I. Mott transition of excitons in coupled quantum wells. PHYSICAL REVIEW LETTERS 2008; 100:256402. [PMID: 18643682 DOI: 10.1103/physrevlett.100.256402] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2007] [Revised: 04/19/2008] [Indexed: 05/26/2023]
Abstract
In this work we study the phase diagram of indirect excitons in coupled quantum wells and show that the system undergoes a phase transition to an unbound electron-hole plasma. This transition is manifested as an abrupt change in the photoluminescence linewidth and peak energy at some critical power density and temperature. By measuring the exciton diamagnetism, we show that the transition is associated with an abrupt increase in the exciton radius. We find that the transition is stimulated by the presence of direct excitons in one of the wells and show that they serve as a catalyst of the transition.
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Affiliation(s)
- M Stern
- Department of Condensed Matter Physics, The Weizmann Institute of Science, Rehovot, Israel.
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Mouchliadis L, Ivanov AL. Anti-trapping of indirect excitons by a current filament. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2007; 19:295215. [PMID: 21483067 DOI: 10.1088/0953-8984/19/29/295215] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
In order to explain the photoluminescence (PL) of indirect excitons collected from localized spots in experiments with a defocused laser excitation of coupled quantum wells (QWs), we model the in-plane carrier transport and charge distribution with a set of drift-diffusion, Poisson and thermalization equations. The quantum statistical corrections are included in our description via a generalized Einstein relationship and quantum mass action law. The PL spots are attributed to transverse current filaments crossing the structure and injecting electrons in the coupled QWs. The accumulated electron charge forms an anti-trap for indirect excitons. Our model quantitatively reproduces the whole set of the relevant experimental data.
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Affiliation(s)
- L Mouchliadis
- Department of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA, UK
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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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Baas A, Karr JP, Romanelli M, Bramati A, Giacobino E. Quantum degeneracy of microcavity polaritons. PHYSICAL REVIEW LETTERS 2006; 96:176401. [PMID: 16712316 DOI: 10.1103/physrevlett.96.176401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2004] [Indexed: 05/09/2023]
Abstract
We investigate experimentally one of the main features of a quantum fluid constituted by exciton polaritons in a semiconductor microcavity, that is, quantum degeneracy of a macroscopic fraction of the particles. We show that resonant pumping allows us to create a macroscopic population of polaritons in one quantum state. Furthermore, we demonstrate that parametric polariton scattering results in the transfer of a macroscopic population of polariton from one single quantum state into another one. Finally, we briefly outline a simple method which provides direct evidence of the first-order spatial coherence of the transferred population.
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Affiliation(s)
- A Baas
- Laboratoire Kastler Brossel, Université Paris 6, Ecole Normale Supérieure et CNRS, UPMC Case 74, France.
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Li JJ, Tsay JM, Michalet X, Weiss S. Wavefunction engineering: From quantum wells to near-infrared type-II colloidal quantum dots synthesized by layer-by-layer colloidal epitaxy. Chem Phys 2005; 318:82-90. [PMID: 22865949 DOI: 10.1016/j.chemphys.2005.04.029] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
We review the concept and the evolution of bandgap and wavefunction engineering, the seminal contributions of Dr. Chemla to the understanding of the rich phenomena displayed in epitaxially grown quantum confined systems, and demonstrate the application of these concepts to the colloidal synthesis of high quality type-II CdTe/CdSe quantum dots using successive ion layer adsorption and reaction chemistry. Transmission electron microscopy reveals that CdTe/CdSe can be synthesized layer by layer, yielding particles of narrow size distribution. Photoluminescence emission and excitation spectra reveal discrete type-II transitions, which correspond to energy lower than the type-I bandgap. The increase in the spatial separation between photoexcited electrons and holes as a function of successive addition of CdSe monolayers was monitored by photoluminescence lifetime measurements. Systematic increase in lifetimes demonstrates the high level of wavefunction engineering and control in these systems.
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Affiliation(s)
- J Jack Li
- Department of Chemistry and Biochemistry, University of California at Los Angeles, 607 Charles E Young Drive East, Los Angeles, CA 90095, USA
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10
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Balatsky AV, Joglekar YN, Littlewood PB. Dipolar superfluidity in electron-hole bilayer systems. PHYSICAL REVIEW LETTERS 2004; 93:266801. [PMID: 15698002 DOI: 10.1103/physrevlett.93.266801] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2004] [Indexed: 05/24/2023]
Abstract
Bilayer electron-hole systems, where the electrons and holes are created via doping and are confined to separate layers, undergo excitonic condensation when the distance between the layers is smaller than the typical distance between the particles within the layer. We argue that the excitonic condensate is a novel dipolar superfluid in which the phase of the condensate couples to the gradient of the vector potential. We predict the existence of a dipolar supercurrent which can be tuned by an in-plane magnetic field. Thus the dipolar superfluid offers an example of excitonic condensate in which the composite nature of its constituent excitons is manifest in the macroscopic superfluid state. We also discuss various properties of this superfluid including the role of vortices.
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Affiliation(s)
- Alexander V Balatsky
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87544, USA
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11
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Lee C. Bose-Einstein condensation of particle-hole pairs in ultracold fermionic atoms trapped within optical lattices. PHYSICAL REVIEW LETTERS 2004; 93:120406. [PMID: 15447239 DOI: 10.1103/physrevlett.93.120406] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2004] [Indexed: 05/24/2023]
Abstract
We investigate the Bose-Einstein condensation (BEC, superfluidity) of particle-hole pairs in ultracold fermionic atoms with repulsive interactions and arbitrary polarization, which are trapped within optical lattices. In the strongly repulsive limit, the dynamics of particle-hole pairs can be described by a hard-core Bose-Hubbard model. The insulator-superfluid and charge-density-wave- (CDW) superfluid phase transitions can be induced by decreasing and increasing the potential depths with controlling the trapping laser intensity, respectively. The parameter and polarization dependence of the critical temperatures for the ordered states (BEC and/or CDW) are discussed simultaneously.
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Affiliation(s)
- Chaohong Lee
- Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Strasse 38, D-01187 Dresden, Germany.
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12
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Perali A, Pieri P, Strinati GC. Quantitative comparison between theoretical predictions and experimental results for the BCS-BEC crossover. PHYSICAL REVIEW LETTERS 2004; 93:100404. [PMID: 15447391 DOI: 10.1103/physrevlett.93.100404] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2004] [Indexed: 05/24/2023]
Abstract
Theoretical predictions for the Bardeen-Cooper-Schrieffer-Bose-Einstein condensation crossover of trapped Fermi atoms are compared with recent experimental results for the density profiles of 6Li. The calculations rest on a single theoretical approach that includes pairing fluctuations beyond mean-field. Excellent agreement with experimental results is obtained. Theoretical predictions for the zero-temperature chemical potential and gap at the unitarity limit are also found to compare extremely well with Quantum Monte Carlo simulations and with recent experimental results.
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Affiliation(s)
- A Perali
- Dipartimento di Fisica, Università di Camerino, I-62032 Camerino, Italy
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Affiliation(s)
- J P Eisenstein
- California Institute of Technology, Pasadena, CA 91125, USA.
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