Magnetic-field-induced resonance in four-wave mixing in GaAs.

Abstract

The frequency-domain four-wave-mixing response of excitons in GaAs in a magnetic field is theoretically and experimentally studied. For linearly cross-polarized excitation beams, the application of a magnetic field induces a resonance that leads to the observation of a narrow dip in the primary resonance. The primary resonance has a width given by the exciton spin-flip rate while the narrow dip has a width determined by the recombination rate. The results reflect the dynamics of two observables defined in terms of the appropriate Fourier components of the net population and the net population transfer between the two oppositely spin-oriented excitonic states, similar to the normal decay modes of the system. The relative amplitude of these observables is determined by the relative polarization of the incident fields and the strength of the applied magnetic field.