Spin-split subbands and magneto-oscillations in III-V asymmetric heterostructures

A quantum-mechanical study of the magneto-oscillations in asymmetric heterostructures is presented with the aim of clarifying the origin and the effects of the spin-orbit spin splitting in the conduction subband. The magnetization of the two-dimensional electron gas at the interface of modulation-doped III-V semiconductor heterojunctions is calculated as a function of applied magnetic field and carrier concentration, taking into account both spin-orbit (zero-field) spin-splitting contributions: one due to the ${\mathit{k}}^3$ bulk term and one due to the lack of specular symmetry ${\mathrm{\sigma }}_{\mathit{h}}$ along the growth direction. Regular beating patterns in the amplitude of the oscillations are shown to originate from the latter term. The ${\mathit{k}}^3$ term introduces a k-space anisotropy in the zero-field spin splitting. This leads to anomalous beating patterns, related to the occurrence of a magnetic breakdown at special points of the Fermi surface with a small spin splitting. Experimental evidence of regular beating patterns has been found in InAs-based heterostructures. The possibility of observing anomalous beating patterns in GaSb heterojunctions is discussed.