MAGNETIC-FIELD-ENHANCED OUTGOING EXCITONIC RESONANCE IN MULTIPHONON RAMAN-SCATTERING FROM POLAR SEMICONDUCTORS

A combined scattering mechanism involving the states of free electron- hole pairs (exciton continuum) and discrete excitons as intermediate s tates in the multi-phonon Raman scattering leads to (i) a strong incre ase of the scattering efficiency in the presence of a high magnetic fi eld and to (ii) an outgoing excitonic resonance. The two features are not compatible when only uncorrelated pairs (leading only to a strong increase of the scattering efficiency under the applied magnetic field ) or discrete excitons (resulting in the outgoing resonance at the exc itonic gap) are taken into account.