Islands of exciton condensed phases in a two-dimensional system, the distribution of their sizes and coherence in position

Electron-Hole Distribution and Exciton Condensed Phase Formation in Semiconductor Quantum Wells

“…With lowering the temperature, the ring remains fragmented. These results agree with the statistical calculations [6] and the experiments [1][2][3][4].…”

“…To study the problem of exciton condensation afterwards, we use the results of calculations of the exciton generations rate G, obtained in [3,4,6]. As it is shown in Refs.…”

“…At present, there are two models explaining the appearance of a fragmented ring in the emission around the laser spot [5,6]. According to [5], the presence of excitons on the lowest level stimulates exciton relaxation and transition to this level owing to bosonic character of exciton statistics.…”

“…This model has a problem with the correct prediction of the temperature of the ring fragmentation, because in the experiment [1] the fragmentation is observed at higher temperature (or at smaller exciton density) than the theory predicts. The model [6] was based on the traditional phase transition theory, generalized for the case of a non-equilibrium system, in which created particles (excitons) have finite lifetimes. The condensation takes place in real space, not in momentum space at k = 0, i.e., the condensed phase is not the Bose-Einstein condensate.…”

“…Our approximation allows to take into account inhomogeneity of the system (the generation rate is an essentially inhomogeneous function of coordinates) and to obtain new results, e.g., a description of a transition from a fragmented to a continuous structure of luminescence ring with changing parameters of the system, the irradiation of the system by two spatially separated laser spots, etc. To solve these problems using a stochastic approach [6] would be very complicated.…”