Bose-Einstein statistics in thermalization and photoluminescence of quantum-well excitons

Abstract

Quasi-equilibrium relaxational thermodynamics is developed to understand LA-phonon-assisted thermalization of Bose-Einstein distributed excitons in quantum wells. We study the quantumstatistical effects in the relaxational dynamics of the effective temperature of excitons T = T (t). When T is less than the degeneracy temperature T0, well-developed Bose-Einstein statistics of quantum well excitons leads to nonexponential and density-dependent thermalization. At low bath temperatures T b → 0 the thermalization of quantum-statistically degenerate excitons effectively slows down and T (t) ∝ 1/ ln t. We also analyze the optical decay of Bose-Einstein distributed excitons in perfect quantum wells and show how nonclassical statistics influences the effective lifetime τopt. In particular, τopt of a strongly degenerate gas of excitons is given by 2τR, where τR is the intrinsic radiative lifetime of quasi-two-dimensional excitons. Kinetics of resonant photoluminescence of quantum well excitons during their thermalization is studied within the thermodynamic approach and taking into account Bose-Einstein statistics. We find density-dependent photoluminescence dynamics of statistically degenerate excitons. Numerical modeling of the thermalization and photoluminescence kinetics of quasi-two-dimensional excitons are given for GaAs/AlGaAs quantum wells.78. 72.10.Di; 63.20.Kr

Pattern formation in the exciton inner ring

“…In the case of nonresonant excitation, heating of the exciton gas occurs due to the injection of high-energy excitons, which then thermalize within a time scale much shorter than the cooling time associated with acoustic phonons. 57 The laser-induced heating rate S laser (T 0 ,T , pump(probe) ,E (ex) pump(probe) ) is characterized by the injection rate pump(probe) and the excess energy E (ex) pump(probe) acquired by photoexcited excitons due to the pump (probe) beams. The excess energy relates to the laser excitation energy E pump(probe) by E (ex) pump(probe) = E pump(probe) − E I X where E I X is the indirect exciton energy.…”

Trapping of Cold Excitons in Quantum Well Structures with Laser Light

“…1c-e and 2a, for low excitation powers the PL profile follows the laser excitation ring; however, with increasing excitation power a spatial PL peak emerges at the center of the laser excitation ring, indicating the accumulation of a cold and dense exciton gas. The exciton degeneracy at the trap center N E=0 = exp(T 0 /T ) − 1, where [26], can be estimated from the exciton density and temperature.…”

Abrupt barrier contribution to electron spin splitting in asymmetric coupled double quantum wells

“…The Gaussian halfwidth γ is related to the scattering and relaxation processes and, thus, to the temperature [19]. Expressions (23,24) are valid provided the interband velocity v cv does not depend on in-plane momentum.…”