Anisotropic Magnetoresistance of Two-Dimensional Holes in GaAs

Experiments on high-quality GaAs (311)A two-dimensional holes at low temperatures reveal a remarkable dependence of the magnetoresistance, measured with an in-plane magnetic field ( $B$), on the direction of $B$ relative to both the crystal axes and the current direction. The magnetoresistance features, and in particular the value of $B$ above which the resistivity exhibits an insulating behavior, depend on the orientation of $B$. To explain the data, the anisotropic band structure of the holes and a repopulation of the spin subbands in the presence of $B$, as well as the coupling of the orbital motion to $B$, need to be taken into account.