Induced coherent macroscopic states of excitons and biexcitons in a microcavity-embedded Zn 1- xCd xSe-type quantum well

The conditions of induced and spontaneous Kosterlitz-Thouless-type Bose-Einstein condensation (BEC) of excitons and biexcitons in a microcavity-embedded quantum well are discussed. As an example the Zn _{1- x}Cd _xSe/ZnSe quantum well is considered, where the HH-exciton electronic structure consisting of four types of excitons - E( x), E( y), A₁, A₂ is taken into account. A polarized strong pump pulse with the frequency in the polariton region induces the BEC of polaritons and biexcitons. The biexciton is formed from the above-mentioned four types of excitons. The coherent polariton and biexciton concentration were obtained. It was proved that if the cavity photon mode E_ph(0) is below the exciton resonance E_ex(0), the biexciton is always polarized. If E_ph(0)> E_ex(0) and the pump frequency is in the electron-hole transition region, optical nonactive A₁, A₂ HH-excitons can be accumulated and spontaneous Kosterlitz-Thouless-type BEC of biexcitons and “dark” excitons can occur.