THEORY OF COHERENTLY DRIVEN BIEXCITONS IN STRONG MAGNETIC-FIELDS

A new regime at low excitation densities which is not in accordance wi th the semiconductor Bloch equations lias been revealed in recent expe riments on fs time-resolved coherent wave mixing under high magnetic f ield. We present a rigorous theory of strongly correlated magneto-exci tons which is based on the coherent truncation scheme. Due to the rest riction of excitonic degrees of freedom by the magnetic field Coulomb correlation effects are strongly enhanced. Om numerical results for Ga As explain most of the experimental findings. Especially we can show t hat the slow rising time of the time-integrated four-wave mixing signa ls results from the non-Markovian coupling of the polarization to biex citonic continuum states.