Anomalous magnetoresistance peak in (110) GaAs two-dimensional holes: Evidence for Landau-level spin-index anticrossings

We measure an anomalous magnetoresistance peak within the lowest Landau level ( ν = 1) minimum of a two-dimensional hole system on (110) GaAs. Self-consistent calculations of the valence band mixing show that the two lowest spin-index Landau levels anticross in a perpendicular magnetic field B consistent with where the experimental peak is measured, B p . The temperature dependence of the anomalous peak height is interpreted as an activated behavior across this anticrossing gap. Calculations of the spin polarization in the lowest Landau levels predict a rapid switch from about − 3 / 2 to +3 / 2 spin at the anticrossing. The peak position B p is shown to be affected by the confinement electrostatics, and the utility of a tunable anticrossing position for spintronics applications is discussed.