A giant shot of radiation intensity as eventual evidence of Bose-Einstein condensation of excitons in double quantum wells in GaAs/AlGaAs

Abstract

In this paper we present a low-temperature (T < 30 K) photoluminescence (PL) study of space-indirect excitons in GaAs/AlGaAs double quantum wells at pumping density P and external electric field V dc . At certain external parameter values (P , T and V dc ) part of the spectral profile of the indirect exciton (IX) line reveals an enormous increase (shot) of PL intensity (threefold), which fluctuates in time on the characteristic scale of tens of seconds. To explain this anomalous behaviour we use the theoretical model of the Bose-Einstein condensation effect which takes place in a system of 2D bosons which, in addition to extended states, have a discrete energy spectrum below the bottom of the free zone.

Spontaneous Symmetry Breaking and Coherence in Two-Dimensional Electron–Hole and Exciton Systems

“…Thus the spectral profile of the IX line corresponding to the case of figure (d) was shown on a large scale in the figure 3 of Ref. [142] and it is reproduced here in Fig.4. It has some interesting peculiarities consisting of a narrow intense line C and of 'wings' W having significantly smaller intensity.…”

“…Figure 1 of the Ref. [142] is reproduced in Fig.3. It shows the luminescence spectra of the DQW, dependent on V dc at T = 1.8K and the density of optical excitation P = 5W cm −2 .…”

“…In these systems the polariton lifetime is longer than, but not much longer than the polariton-polariton scattering time, which leads to the thermalization. By contrast over past twenty years several groups of investigators represented by Snoke [111][112][113][114][115][116][117][118][119][120][121], Butov [122][123][124][125][126][127][128][129][130], Timofeev [131][132][133][134][135][136][137][138], Krivolapchuk [139][140][141][142][143], Fukuzawa [144][145][146] and their coworkers have pursued experiments in double quantum well (DQW) excitonic systems with very long lifetime. In these systems the indirect excitons (IXs) formed from spatially separated electrons and holes have dipole moments oriented perpendicularly to the layers.…”

“…PL spectra taken at T = 1.8K, P = 5W cm −2 and V dc = 0 V(a), -0.5 V(b), -2 V(c). The inset shows the indirect regime of the DQW following the Ref [142]…”

Magnetoexciton states inGaAs/Ga0.7Ríos1, Porras‐Montenegro2 2003Phys. Rev. B

“…Mathos et al 5 have studied the diamagnetic shift, of the 1S-like and 2S-like states of excitons, in symmetric DQW system using the fractional-dimensional approach. Others authors [8][9][10][11][12][13] have been focused on studying the effects of the temperature, electric field, and bosonic condensation on these systems.…”