SPIN-SPLIT SUBBANDS AND MAGNETO-OSCILLATIONS IN III-V ASYMMETRIC HETEROSTRUCTURES

A quantum-mechanical study of the magneto-oscillations in asymmetric h eterostructures is presented with the aim of clarifying the origin and the effects of the spin-orbit spin splitting in the conduction subban d, The magnetization of the two-dimensional electron gas at the interf ace of modulation-doped III-V semiconductor heterojunctions is calcula ted as a function of applied magnetic field and carrier concentration, taking into account both spin-orbit (zero-field) spin-splitting contr ibutions: one due to the k(3) bulk term and one due to the lack of spe cular symmetry sigma(k) along the growth direction. Regular beating pa tterns in the amplitude of the oscillations are shown to originate fro m the latter term. The k(3) term introduces a k-space anisotropy in th e zero-held 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 heterostructu res. The possibility of observing anomalous beating patterns in GaSb h eterojunctions is discussed.