Spin-resolved femtosecond magnetoexciton interactions in GaAs quantum wells

Abstract
We use femtosecond nonlinear spectroscopy and high magnetic fields to study quantum-well excitonic states of well-defined angular momentum character. Our results show that the femtosecond nonlinear optical response is governed by exciton-exciton interactions that depend on the angular momentum character of the initially excited distribution. Remarkably, optically active excitons at high magnetic field undergo spin relaxation to an optically inactive state.