Spin-orbit and exchange interaction in surface quantum wells on gapless semimagnetic semiconductor HgMnTe

摘要

The first study of two-dimensional electron gas in surface layers on HgMnTewith inverted bands is carried out experimentally and theoretically. It isshown that the structure of investigated capacitance magnetooscillations inHgMnTe MOS structures is fully similar to the one in the non-magneticnarrow-gap semiconductor HgCdTe and the sole effect due to exchange interactionis the temperature shift of beat nodes. The information about exchange effectsis obtained only due to our modeling of oscillations, because any pronouncedchanges in the position of oscillations are not observed and the separate spincomponents are not resolved. The Landau levels are calculated in the frameworkof concept we developed previously for the description of subband dispersionsin zero magnetic field B=0. The new parameters (like those of $T/\sqrt{eB}$)arise in the theory of magnetooscillations in the semiconductors withquasirelativistic spectrum in contrast to the case of parabolic bands. Themodeling shows that the spin-orbit splitting far exceeds a contribution due toexchange interaction. The calculated amplitudes of ``partial'' oscillations fordifferent spin branches of spectrum are essentially different in accordancewith the observed difference in the intensity of corresponding lines in Fourierspectra. The comparison between experiment and theory for differenttemperatures and parameters of exchange interaction is reported. The dominantmechanisms of the scattering responsible for the broadening of Landau levelsare discussed.