Induced coherent macroscopic states of excitons and biexcitons in a microcavity-embedded Zn1−xCdxSe-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 Zn1−xCdxSe/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 Eph(0) is below the exciton resonance Eex(0), the biexciton is always polarized. If Eph(0)>Eex(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.