Mott Transition of Excitons in Coupled Quantum Wells

Stern, Michael; Garmider, V.; Umansky, V.; Bar‐Joseph, I.

doi:10.1103/physrevlett.100.256402

Cited by 67 publications

(71 citation statements)

References 22 publications

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“…Further experiments discovered a very large number of related phenomena and quite rich physics of the system (see Refs. [1,2,3] and references therein). Theory predicts the existence of many phases with different and unusual properties.…”

Section: Introductionmentioning

confidence: 99%

Exciton correlations in coupled quantum wells and their luminescence blue shift

2009

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In this paper we present a study of an exciton system where electrons and holes are confined in double quantum well structures. The dominating interaction between excitons in such systems is a dipole -dipole repulsion. We show that the tail of this interaction leads to a strong correlation between excitons and substantially affects the behavior of the system. Making use of qualitative arguments and estimates we develop a picture of the exciton -exciton correlations in the whole region of temperature and concentration where excitons exist. It appears that at low concentration degeneracy of the excitons is accompanied with strong multi-particle correlation so that the system cannot be considered as a gas. At high concentration the repulsion suppresses the quantum degeneracy down to temperatures that could be much lower than in a Bose gas with contact interaction.We calculate the blue shift of the exciton luminescence line which is a sensitive tool to observe the exciton -exciton correlations. d and the average separation between excitons are assumed to be larger than the exciton radius a X .

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Section: Introductionmentioning

confidence: 99%

Exciton correlations in coupled quantum wells and their luminescence blue shift

2009

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“…photoluminescence spectroscopy. [30][31][32][33] Recent terahertz spectroscopy has shed new light on this problem, [34][35][36][37] making it possible to determine the exciton ionization ratio through the quantitative evaluation of excitons and unbound eh pairs densities. In particular, our recent study on the ultrafast dynamics of EMT in GaAs under the resonant excitation of excitons has indicated the signature of first-order phase transition.…”

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confidence: 99%

Rate Equation Analysis of the Dynamics of First-order Exciton Mott Transition

Sekiguchi

Shimano

2017

J. Phys. Soc. Jpn.

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We performed a rate equation analysis on the dynamics of exciton Mott transition (EMT) with assuming a detailed balance between excitons and unbound electron-hole (e-h) pairs. Based on the Saha equation with taking into account the empirical expression for the band-gap renormalization effect caused by the unbound e-h pairs, we show that the ionization ratio of excitons exhibits a bistability as a function of total e-h pair density at low temperatures. We demonstrate that an incubation time emerges in the dynamics of EMT from oversaturated exciton gas phase on the verge of the bistable region. The incubation time shows a slowing down behavior when the pair density approaches toward the saddle-node bifurcation of the hysteresis curve of the exciton ionization ratio.Photocontrol of condensed matter systems has gained continuing interests over decades, [1][2][3] e.g. in semiconductors, 4,5) Mott insulators, 3,6-9) spin crossover complexes, [10][11][12] and superconductors. 13,14) Among diverse material systems, photoexcited electron-hole (e-h) systems in semiconductors offer a unique arena to study the rich variety of phases emergent in many particle systems, and their non-equilibrium dynamics. 4,15) One of the intriguing aspects of e-h systems is that the strength of inter-particle Coulomb interaction can be effectively controlled by changing the density of photoexcited carriers through the screening effect, by simply changing the excitation light intensity. The change of the Coulomb interaction causes a phase transition, or crossover, from the insulating exciton gas phase in the low density regime to the metallic e-h plasma in the high density regime, referred to as exciton Mott transition (EMT). There is a long-standing argument whether EMT is a crossover or a first-order phase transition accompanied by a bistability at sufficiently low temperatures. [16][17][18][19][20][21][22] In general, bistability appears in diverse systems such as electronic circuits, optoelectronic systems, magnetic systems, molecular and biological systems, etc. Figure

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“…[22]. The phase diagram of indirect excitons formed by the spatially separated electrons and holes in GaAs/AlGaAs CQWs was analyzed experimentally, and it was shown that the exciton system undergoes a phase transition to an unbound electron-hole plasma for increasing temperatures [22].…”

Section: Introductionmentioning

confidence: 99%

On the phase diagram of a two-dimensional electron–hole system

Berman

Kezerashvili

Ziegler

2015

Physica E: Low-dimensional Systems and Nanostructures

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A first order phase transition between a BCS phase and an insulating Mott phase for a gas of spatially separated electrons and holes with tunable Coulomb interaction and variable density is predicted. In the framework of a BCS-like mean-field approach and a Landau expansion in terms of the pairing order parameter the phase diagram is studied. This indicates several phases and phase transitions, including an electron-hole plasma at low density and weak interaction, an intermediate BCS phase with Cooper pairs and an electron-hole plasma at high density and weak interaction. The insulating Mott phase appears for the strong interaction and low temperatures. We briefly discuss the possibilities to realize these phases in realistic systems such as coupled quantum wells and graphene double layers.

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Mott Transition of Excitons in Coupled Quantum Wells

Cited by 67 publications

References 22 publications

Exciton correlations in coupled quantum wells and their luminescence blue shift

Exciton correlations in coupled quantum wells and their luminescence blue shift

Rate Equation Analysis of the Dynamics of First-order Exciton Mott Transition

On the phase diagram of a two-dimensional electron–hole system

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