Self-organization processes at exciton condensation in quantum wells.

The problem of phase transitions in a system of particles with finite value of the lifetime is analyzed. As an example the theory of condensation of indirect excitons in semiconductor double quantum wells is presented. For description of a spatial distribution of condensed and gas phases two models of phase transitions are used: the model of nucleation and growth and the model of spinodal decomposition generalized on unstable particles. It is shown that due to finite value of the exciton lifetime the sizes of condensed phases are restricted and in two-dimensional case, the regions of condensed phase have the shape of islands located within the excitonic gas. There is specific interaction between islands of the condensed phase through exciton concentration fields. This interaction causes the development of different structures of exciton condensed phases in the crystal irradiated by light. The evolution of the islands of condensed phase is studied depending on the changes of the temperature, pumping and the presence of external potential. [ABSTRACT FROM AUTHOR]