Exciton condensation in quantum wells. Exciton hydrodynamics. The effect of localized states

Abstract

The hydrodynamic equations for indirect excitons in the double quantum wells are studied taking into account 1) a possibility of an exciton condensed phase formation, 2) the presence of pumping, 3) finite value of the exciton lifetime, 4) exciton scattering by defects. The threshold pumping emergence of the periodical exciton density distribution is found. The role of localized and free exciton states is analyzed in the formation of emission spectra.

Observation of the exciton Mott transition in the photoluminescence of coupled quantum wells

“…The localized excitons are caused by doping impurities or fluctuations in the quantum-well thickness [53,55,56], which form random localized traps for the excitons. In typical quality samples these traps are saturated with relative ease due to Pauli blocking [53,54] at carrier densities of the order of 10 9 cm −2 below 2 K [57,58], and at even lower densities at higher temperatures [59]. In our measurements, however, the low-energy peak does not reach saturation even at carrier densities of the order of 10 11 cm −2 .…”

“…A mechanism resulting in a somewhat similar PL spectrum is the interplay of localized and free excitons [53,54]. The localized excitons are caused by doping impurities or fluctuations in the quantum-well thickness [53,55,56], which form random localized traps for the excitons.…”

“…The EH-plasma contribution is significant at all excitation intensities, and its lineshape is well reproduced by a Voigt function, see Figs. A mechanism resulting in a somewhat similar PL spectrum is the interplay of localized and free excitons [53,54]. The localized excitons are caused by doping impurities or fluctuations in the quantum-well thickness [53,55,56], which form random localized traps for the excitons.…”

Model of fragmentation of the exciton inner ring in semiconductor quantum wells

“…In the previous studies of the condensed phase, two popular models of the phase transitions were used. We applied the stochastic model of the nucleation-growth (Livshits-Slyosov) in the works 6,8,17 and the model of spinodal decomposition (Kahn-Hillert) in the works 9,16,19,[27][28][29] , modified and generalized for a system of particles with a finite lifetime. For the solution of the problem of the present paper, we applied a modified model of spinodal decomposition.…”

“…32 . The model of the phase transitions of particles with a finite lifetime successfully managed to describe 6,9,16,17,19,[27][28][29] the emission from the ring around the laser spot, observed in Ref. 2 , the emission from the quantum well under the aperture in the electrode, observed in Refs.…”