EXCHANGE INTERACTION IN P-TYPE GAAS ALXGA1-XAS HETEROSTRUCTURES STUDIED BY MAGNETOTRANSPORT/

Low-temperature magnetotransport experiments have been performed on a p-type GaAs/AlxGa1-xAs quantum well. From activation measurements on S hubnikov-de Haas conduction minima it was found that ex change interac tions can be of great importance for both odd and even filling factors and strongly influence the observed periodicity. Furthermore, it was found that the temperature dependence of Shubnikov-de Haas oscillation s in the low-magnetic-field regime could not be explained within a sin gle-particle model based on a solution of the full Luttinger Hamiltoni an in a magnetic field. Numerical simulations of Shubnikov-de Haas spe ctra, based on a model that treats hole exchange interactions in a sim plified manner, show unambiguously that exchange driven enhancement of hole ''spin'' splittings are extremely important at magnetic fields a s low as 1.5 T. Also, the inclusion of a valence-band warping in the c alculations is shown to be essential. Qualitatively, most experimental observations could be described within the presented model. Our resul ts imply that, in any hole system, the effective masses obtained from temperature-dependent SdH measurements are to be treated with extreme care as they can deviate from their single-particle value by as much a s a factor of 2.