A detailed Landau level spectroscopy via activation gap measurements in p-type square (110) GaAs quantum wells

Isik Nebile

Technische Universität München, Germany

N.Isik1, M. Bichler1, S. F. Roth1, A. Fontcuberta i Morral1, G. Abstreiter1, and M. Grayson1,2 1 Walter Schottky Institute, Technische Universität München, D-85748 Germany, 2 Department of Electrical Engineering and Computer Science, Northwestern University, Evanston, IL 60208-3118 USA
In p-type (110) quantum wells, a single anomalous magnetoresistance peak has been shown to be the transport signature of a ± 3/2 spin-reversal level-anticrossing within the lowest Landau level (nu= 1) of a two-dimensional hole system when the confinement is a triangular potential well [1]. On either side of this anticrossing the entire spin population is predicted to change its spin form a +3/2-like ground state to -3/2-like ground state. Recently fabricated 400 A wide square quantum wells show an anticrossing peak at nu = 1 Landau level at lower magnetic field with applying negative top gate bias. Temperature dependence of the peak height is consistent with thermal activation across an anticrossing gap (Egap = 110 µeV ). With the application of a front-gate and back-gate bias, new features are apparent in low Landau levels including nu = 2 and nu= 3 as a function of density, illumination, and back-gate bias. It is therefore interesting to perform a mapping of the Landau level spectrum for these samples by measuring the activated gap energies. Additional studies of the lowest Landau level anticrossing feature will be presented, as well as studies of activation gaps at various other filling factors. The result represents a Landau fan which will be useful for determining heavy-hole/light-hole mixing coefficients in k-dot-p simulations of p-GaAs quantum wells. Data from square-well as well as triangular-well confinement will be presented.
[1] F. Fischer, R. Winkler, D. Schuh, M. Bichler, G. Abstreiter and M. Grayson Phys. Rev. B 75, 073303 (2007).
[2] Winkler, R. Spin Orbit Coupling Effects in Two Dimensional Electron and Hole Systems. Springer Verlag (2003).