Exciton phase transitions in semiconductor quantum wells with disc-shaped electrode

Abstract

Phase transitions in a system of indirect excitons in semiconductor double quantum wells are studied for a set-up when one of the electrodes is of finite size and, in particular, has the shape of a disc. At voltage a region under the rim of the disc is created where excitons have lower energy, thus providing a macroscopic trap attractive for excitons while being repulsive for charged particles. The theory of the formation of patterns of the excitonic condensed phase under the disc is built based on the assumption of the existence of the inter-exciton range where the interaction between them is attractive. The finite value of the exciton lifetime is taken into account serving as a limiting factor for the size of the islands of the condensed phase. The calculations reveal complex restructuring of the patterns of the spatial distribution of exciton density with increasing pumping intensity: from the structureless gaseous phase to separate islands of the condensed phase within the gaseous phase, then to islands of the gaseous phase in the bulk of the condensed phase and finally to the continuous condensed phase.

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

“…The authors made the conclusion [31] that the interaction between excitons is repulsive, and, therefore, the formation of a condensed phase by attractive interaction is impossible. This contradicts the main assumption of our works [19][20][21][22][23][24][25], though these works explain many experiments. Now, we remove this contradiction taking into account the presence of localized excitons.…”

“…Our model is based on the appearance of self-organization processes in non-equilibrium systems for excitons with attractive interaction shown in [2,3]. Investigations performed in this model [19][20][21][22][23][24][25] gave the explanations of spatial structures and their temperature and pumping dependencies obtained in different experiments [4,5,[8][9][10]. Theoretical approaches of the works [19][20][21][22][23][24][25] are based on the following assumptions.…”

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.…”

Pulses of the Excitonic Condensed Phase in Semiconductors with Double Quantum Well at Steady Pumping

“…In addition, the analysis of another experiments was fulfilled. The peculiarities of the appearance of a structure in the luminescence of indirect excitons in the presence of a periodic potential [20] were presented in [21]. The structures that arise in the luminescence from double quantum wells with electrodes of the different form [22,23] were explained in [24].…”