Spin energetics in a GaAs quantum well: Asymmetric spin-flip Raman scattering

We demonstrate an asymmetric dependence of the spin-flip electronic Raman spectrum from a two-dimensional electron gas on the direction of circular polarization of the photons, resulting from an interference of light scattered from longitudinal and transverse spin-density fluctuations. By exploiting these selection rules, we are able to determine experimentally that the sign of the band-structure parameter $a_{42},$ which describes the bulk $k^3$ conduction-band spin splitting in zinc-blende semiconductors, is negative for GaAs.