Condensed Matter and Biological Physics Seminars

An anomalous magnetoresistance peak is observed within the lowest Landau level (nu = 1) of a two-dimensional hole system on (110) GaAs. We interpret this peak as the transport signature of a +/- 3/2 spin-reversal level-anticrossing in the lowest Landau level. +Temperature dependence of the peak height is consistent with thermal activation across an anticrossing gap. Persistent photoconductivity controllably shifts the peak to lower magnetic field by several tesla. Self-consistent calculations of the valence band mixing beyond the usual axial approximation allow the anticrossing magnetic field, anticrossing gap and spin polarization to be evaluated as a function of average confinement electric field. The confinement necessary to explain the observed peak positions before and after illumination is consistent with a dilute photo-charging of the substrate. F. Fischer, R. Winkler, D. Schuh, M. Bichler, G. Abstreiter and M. Grayson Phys. Rev. B 75, 073303 (2007)