Two-dimensional electron-hole system in a strong magnetic field

Abstract

A theory of a two-dimensional electron-hole system in a strong magnetic field is developed. Three different models are considered, whose common distinguishing feature is electron-hole asymmetry. It is shown that this asymmetry influences radically the system properties. It leads to an exciton interaction that does not vanish when the momentum of the exciton relative motion tends to zero. As a result, the scattering amplitude diverges at small momenta, and magnetic biexcitons appear at arbitrarily weak asymmetry. The thermodynamics of such a system in the Hartree-Fock approximation is similar in many respects to the thermodynamics of a monopolar system. The high-temperature phase is the homogeneous one, and the low-temperature phase has the charge density waves. The homogeneous phase with exciton pairing is absolutely unstable.