Highly anisotropic g-factor of two-dimensional hole systems

Coupling the spin degree of freedom to the anisotropic orbital motion of tw o-dimensional (2D) hole systems gives rise to a highly anisotropic Zeeman s plitting with respect to different orientations of an in-plane magnetic fie ld B relative to the crystal axes. This mechanism has no analog in the bulk band structure. We obtain good, qualitative agreement between theory and e xperimental data, taken in GaAs 2D hole systems grown on (113) substrates, showing the anisotropic depopulation of the upper spin subband as a functio n of in-plane B.