Dresden 2011 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 89: Optical Properties II

HL 89.12: Talk

Friday, March 18, 2011, 13:15–13:30, POT 251

Zero-magnetic-field spin-splitting and the warping in the valence band of highly p-doped asymmetric AlGaAs/GaAs Quantum Wells — •Michael Hirmer, M. Hirmer, D. Schuh, W. Wegscheider, T. Korn, and C. Schüller — Institut für Experimentelle Physik, Universität Regensburg, 93040 Regensburg

Zero-Magnetic-Field-Spin-Splitting (ZMFSS) in 2D quantum wells (QW) induced by the structure inversion asymmetry, and its control, are of major importance for both fundamental research and spintronic applications. In hole systems, the asymmetry leads to a ZMFSS of the heavy hole (HH) states in third order of the in-plane wave vector k_|| [1]. In our experiments, we focus on highly p-doped asymmetric AlGaAs/GaAs QW. We utilize electronic intersubband Raman measurements in backscattering geometry. In all samples we observe a low-energy spin-density excitation (SDE) with energies in the range of 0-3 meV. Samples with higher hole density show a two-component SDE. Comparing these excitation energies to 8 band k·p calculations [2] of the valence subbands , the SDE can be interpreted as an intersubband excitation of the spin-split HH ground state, reflecting directly the ZMFSS. The two components can be attributed to different HH dispersions in different crystallographic directions, the so-called warping. We found that the observed spin splitting increases systematically with increasing hole density p, or by an external electric field. Measurements of the Shubnikov de Haas oscillations showed similar results.

[1] R. Winkler, Phys. Rev. B 62, 073309 (2000).

[2] Nextnano³ by Stefan Birner