Excitonic binding in coupled quantum wells

Szymańska, M. H.; Littlewood, P. B.

doi:10.1103/physrevb.67.193305

Cited by 65 publications

(61 citation statements)

References 18 publications

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“…For N ¼ 2 we find r x ¼ 2.50 nm ¼ 2.43a x and E ind ¼ 87 meVE0.6 Ry x . This binding energy is an order of magnitude larger than E ind ¼ 4-10 meV typical for excitons in GaAs/AlGaAs CQW structures 29,34 .…”

Section: Methodsmentioning

confidence: 97%

High-temperature superfluidity with indirect excitons in van der Waals heterostructures

2014

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All known superfluid and superconducting states of condensed matter are enabled by composite bosons (atoms, molecules and Cooper pairs) made of an even number of fermions. Temperatures where such macroscopic quantum phenomena occur are limited by the lesser of the binding energy and the degeneracy temperature of the bosons. High-critical temperature cuprate superconductors set the present record of B100 K. Here we propose a design for artificially structured materials to rival this record. The main elements of the structure are two monolayers of a transition metal dichalcogenide separated by an atomically thin spacer. Electrons and holes generated in the system would accumulate in the opposite monolayers and form bosonic bound states-the indirect excitons. The resultant degenerate Bose gas of indirect excitons would exhibit macroscopic occupation of a quantum state and vanishing viscosity at high temperatures.

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Section: Methodsmentioning

confidence: 97%

High-temperature superfluidity with indirect excitons in van der Waals heterostructures

2014

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“…In this case only one in-plane mass is relevant at low temperature. This figure also shows a curve for the same parameters but Ry = 4 meV, with the same exciton Bohr radius, which are realistic parameters for indirect excitons in double quantum wells, which have been used in recent experiments [13,14]. It is perhaps surprising that excitons exist all the way up to 100 K or above at these densities.…”

Section: Calculations For a Two-dimensional Systemmentioning

confidence: 96%

Predicting the ionization threshold for carriers in excited semiconductors

Snoke¹

2008

Solid State Communications

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A simple set of formulas is presented which allows prediction of the fraction of ionized carriers in an electron-hole-exciton gas in a photoexcited semiconductor. These results are related to recent experiments with excitons in single and double quantum wells.Many researchers in semiconductor physics talk of "the" Mott transition density in a system of excitons and electron-hole plasma, but do not have a clear handle on exactly how to predict that density as a function of temperature and material parameters in a given system. While numerical studies have been performed for the fraction of free carriers as a function of carrier density and temperature [1, 2], these do not give a readily-accessible intuition for the transition. In this paper I present a simple approach which does not involve heavy numerical methods, but is still fairly realistic. The theory is based on two well-known approximations, which are the massaction equation for equilibrium in when different species can form bound states, and the static (Debye) screening approximation. In addition, simple approximations are used for numerical calculations of the excitonic Rydberg as a function of screening length.

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“…In the opposite limit of photon coupling, the system of spatially-indirect excitons (IXs) in a pair of coupled quantum wells (CQWs) interacts only very weakly with photons [9][10][11] . Indirect excitons, also often referred to as interwell excitons, are comprised of conduction-band electrons and valence-band holes forced by an electric field to reside in adjacent wells, separated spatially in the wafer growth direction.…”

Section: Introductionmentioning

confidence: 99%

Strain-induced darkening of trapped excitons in coupled quantum wells at low temperature

et al. 2011

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In GaAs/AlGaAs coupled quantum wells, strain-induced traps may be used to confine excitons in in-plane, harmonic traps. Using these traps, we have pursued Bose-Einstein condensation (BEC) of long-lived, spatially-indirect excitons. Here, we report a remarkable transition of the indirect exciton luminescence pattern with increasing strain, increasing exciton density, and decreasing temperature, to a spatial pattern exhibiting a large dark spot at trap center, where we expect the exciton density to be maximum. The mechanism of particle loss is ruled out as an explanation for this dark spot. While the onset criteria are approximately consistent with the conditions for BEC of a weakly interacting gas, the conspicuous proximity in energy of the indirect light-hole states suggests that an explanation employing the single-particle physics of light-hole/heavy-hole mixing may explain the phenomenon. The effect of the strain is modeled, and the resulting landscape of indirect exciton spin states is discussed. The relative oscillator strengths of these states are predicted by an exact numerical solution of the two-particle Schrodinger equation for electrons and holes in coupled quantum wells and an electric field. The contrast in oscillator strengths is sufficient to produce this luminescence pattern, but this analysis suggests a strongly diminished lifetime as stress is increased. The opposite lifetime dependence is observed experimentally. Additionally, the temperature dependence eludes explanation by this mechanism.

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Excitonic binding in coupled quantum wells

Cited by 65 publications

References 18 publications

High-temperature superfluidity with indirect excitons in van der Waals heterostructures

High-temperature superfluidity with indirect excitons in van der Waals heterostructures

Predicting the ionization threshold for carriers in excited semiconductors

Strain-induced darkening of trapped excitons in coupled quantum wells at low temperature

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