Collective properties of spatially indirect excitons in asymmetric GaAs/AlGaAs double quantum wells

Krivolapchuk, V. V.; Moskalenko, E. S.; Zhmodikov, A. L.; Cheng, T.S.; Foxon, C.T.

doi:10.1016/s0038-1098(99)00162-3

Cited by 34 publications

(24 citation statements)

References 8 publications

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“…[16,17,18]), the total profile is in very good agreement with the TF inverted parabola (see Fig. 5(a)) [38].…”

supporting

confidence: 56%

“…Moreover, in the structures studied in Refs. [16,17,18] at typical exciton density, e.g., n = 5 · 10 10 cm −2 two peaks in the structure factor and three bumps of the pair distribution function are clearly visible.(iv) The excitation spectrum strongly deviates from the weakly-correlated Bogoliubov prediction although, even in the crossover between exciton and e-h regimes, there is still no roton minimum as found in Refs. [16,17,18].…”

mentioning

confidence: 58%

“…Lk, 03.75.Hh, 02.70.Ss, 73.21.Fg Two-dimensional (2D) dipolar excitons (DEs) with spatially separated electrons (e) and holes (h) are extremely interesting due to increased lifetime, which permits to achieve different quasi-equilibrium exciton phases predicted for the system, e.g., 2D DE superfluid in extended systems [1, 2,3,4,5] [14,15,16,17,18,19] and SQW [20].…”

mentioning

confidence: 99%

“…DE systems can be created in coupled quantum wells (CQWs) [1] or in a single quantum well (SQW) applying a large external electric field (see theory in [13]). At present, a large experimental progress has been achieved in the study of 2D DE collective properties in CQWs [14,15,16,17,18,19] and SQW [20].…”

mentioning

confidence: 99%

“…[16,17,18] at dimensionless densities 1/4 n 4. At the lowest densitȳ n = 1/256 of our computation the superfluid crossover temperature in the DE system of Ref.…”

mentioning

confidence: 99%

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Strong correlation effects in 2D Bose–Einstein condensed dipolar excitons

Lozovik

Kurbakov

Astrakharchik

et al. 2007

Solid State Communications

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By doing quantum Monte Carlo ab initio simulations we show that dipolar excitons, which are now under experimental study, actually are strongly correlated systems. Strong correlations manifest in significant deviations of excitation spectra from the Bogoliubov one, large Bose condensate depletion, short-range order in the pair correlation function, and peak(s) in the structure factor.PACS numbers: 71.35. Lk, 03.75.Hh, 02.70.Ss, 73.21.Fg Two-dimensional (2D) dipolar excitons (DEs) with spatially separated electrons (e) and holes (h) are extremely interesting due to increased lifetime, which permits to achieve different quasi-equilibrium exciton phases predicted for the system, e.g., 2D DE superfluid in extended systems [1, 2,3,4,5] [14,15,16,17,18,19] and SQW [20].The superfluidity and coherent properties of equilibrium e-h systems (in a sense of "spatially separated semimetal") have been also theoretically studied [1, 2,4,11]. An important progress was achieved by studying an electron bilayer in high magnetic field with 1/2 + 1/2 filling of Landau levels [21]. It can be proved that the properties of the system can be presented as a BCS state of a spatially separated (composite fermion) e-h system at zero magnetic field [1, 2,22]. The predicted e-h superfluidity and Josephson-like effects in this system were observed later on experimentally [23]. It is worth noticing that the 2D dipolar Bose systems under consideration have been recently realized in atomic systems with large dipolar moments (e.g., for Cr atoms) [24] and polar molecules [25].The majority of theoretical models describe the excitonic Bose condensate as an ideal or weakly correlated gas. Unfortunately, these approaches have a very limited region of applicability. Indeed, at small densities the repulsive dipole-dipole potential can be described by one parameter a, the s-wave scattering length, and the properties are expected to be universal, i.e., to be the same for all interaction potentials having the same value of scattering length and, in particular, to be the same as in a system of hard-disks of diameter a. In fact, the latter is known to be weakly correlated only in ultra-rarified systems [7]. So, the model of weakly correlated excitons holds only in ultra-rarified gases which have extremely low critical temperature. For real experimental excitonic densities such models can provide only a qualitative description. Thus, a more accurate model should be worked out and a more precise study should be done in order to describe 2D DEs in quantum wells (QWs).This paper is devoted to a detailed microscopic study of 2D DEs by means of the diffusion Monte Carlo (DMC) technique. We prove that excitons are in fact strongly correlated in all the main up-to-now experiments with CQW [16,17,18] in which low-temperature collective effects in exciton luminescence have been observed. We have obtained the following results supporting this fact:(i) The dimensionless compressibility ζ = (m 3 /2π 2 )/χ and the contribution of dipole-dipole collisions to the chemical...

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“…[16,17,18]), the total profile is in very good agreement with the TF inverted parabola (see Fig. 5(a)) [38].…”

supporting

confidence: 56%

mentioning

confidence: 58%

mentioning

confidence: 99%

mentioning

confidence: 99%

“…[16,17,18] at dimensionless densities 1/4 n 4. At the lowest densitȳ n = 1/256 of our computation the superfluid crossover temperature in the DE system of Ref.…”

mentioning

confidence: 99%

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Strong correlation effects in 2D Bose–Einstein condensed dipolar excitons

Lozovik

Kurbakov

Astrakharchik

et al. 2007

Solid State Communications

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Collective behavior of interwell excitons laterally confined in GaAs/AlGaAs double quantum wells

Gorbunov¹,

Тимофеев²

2005

phys. stat. sol. (c)

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PACS 73.21.Fg, 78.55.Cr, 78.67.De The luminescence of interwell excitons laterally confined by long range potential fluctuations and with the use of inhomogeneous electric field in n-i-n GaAs/AlGaAs heterostructures double quantum wells has been investigated under variation of excitation power and temperature. Above mobility threshold very narrow interwell exciton line has been observed and its intensity decrease is linearly dependent on temperature growth. The observed phenomena, which were critical to exciton density and temperature, are attributed to the Bose-condensation in laterally confined quasi-two dimensional system of interwell excitons. 1.In the recent years, the interest in the Bose-Einstein condensation (BEC) of excitons has been stimulated by impressive achievements concerned with the observation and investigation of this phenomenon in dilute and deeply cooled gases of atoms confined within magnetic traps [1]. Because of the large atomic masses, the critical temperatures of the BEC in diluted gases of atoms are of the order of micro Kelvin or even lower. In the case of semiconductors, a hydrogen-like exciton, being a composite boson in principal, has a mass that is several orders of magnitude lower. Due to that, the BEC condensation in a dilute gas of hydrogen-like excitons is expected to occur at much higher temperatures of about 1 K. In the last decade, BEC of excitons in 2D system based on semiconductor heterostructures has been the object of intensive research [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Interwell excitons with electrons and holes spatially separated between adjacent quantum wells in double quantum well heterostructures are in the focus of interests [5][6]. An interest in such systems was stimulated by theoretical studies carried out as early as mid 70s and by recent experimental investigations [2, 5-16]. The system of excitons in coupled quantum wells is very attractive for BEC in many aspects, and, first of all, because the interwell exciton lifetime can be controlled by external bias and is long enough, allowing the excitons to reach thermal quasi-equilibrium with each other. However, it should be recalled that an ideal and infinite (laterally unconfined) 2D system cannot undergo Bose-condensation at nonzero temperatures because number of states diverges when the chemical potential µ → 0. Besides, it is pertinent to recall that according to Bogolubov-Hoenberg theorem an ideal 2D system cannot have a nonzero order parameter because it is destroyed by fluctuations. Nevertheless, the Bose-condensation can occur at nonzero temperatures in quasi-2D systems and 2D systems with lateral confinement. The critical temperature of BEC in spatially confined 2D system, where number of states is finite and spectrum is discrete, is equal to T C ≈ 2ћπN 2 S /gm·log(N S ·S), i.e. logarithmically decreases with increasing the restricted area S filled with a 2D Bose-gas (N S -density, meffective mass of Bose-particle, g -degeneracy of ground excitonic state). A major differe...

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Kinetics of a low density system of indirect excitons in double quantum wells

Yudson¹

2001

Springer Proceedings in Physics

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Collective properties of spatially indirect excitons in asymmetric GaAs/AlGaAs double quantum wells

Cited by 34 publications

References 8 publications

Strong correlation effects in 2D Bose–Einstein condensed dipolar excitons

Strong correlation effects in 2D Bose–Einstein condensed dipolar excitons

Collective behavior of interwell excitons laterally confined in GaAs/AlGaAs double quantum wells

Kinetics of a low density system of indirect excitons in double quantum wells

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