Regensburg 2004 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 22: Transport im hohen Magnetfeld/Quanten-Hall-Effekt
HL 22.4: Vortrag
Dienstag, 9. März 2004, 16:00–16:15, H14
Spectroscopy of energy gaps between landau bands in the vicinity of a thin tunnelling barrier — •M. Habl1, W. Wegscheider1, D. Schuh2, M. Bichler2, and G. Abstreiter2 — 1Institut für Experimentelle und Angewandte Physik, Universität Regensburg, 93040 Regensburg — 2Walter Schottky Institut, Technische Universität München, 85748 Garching
Studying the transport of two laterally adjacent two-dimensional electron systems separated by an atomically precise extended barrier with a thickness in the order of the magnetic length is made possible by the method of cleaved edge overgrowth [1]. For high barriers there are small energy gaps (Δ≪ℏωc) at the crossing points of the bent Landau bands of the left and the right electron systems due to the weak coupling of the counter propagating opposite edge channels. We present the solutions of the Schrödinger equation for the whole system in the one electron approximation which is especially interesting in the low barrier regime (e.g. V0=3 ℏωc) when the results strongly deviate from more crude approximations. For low aluminium concentrations in the AlGaAs barrier the dispersion relation can no longer be calculated as a superposition of two symmetric Landau spectra. Instead a complete numerical calculation must be performed in order to find the correct gaps and their positions. Our theoretical results are compared to experimental data of CEO samples which reveal energy gaps bigger and at different filling factors than expected. The project is supported by the DFG Schwerpunktsprogramm 1092 Quanten-Hall-Systeme.
[1] W. Kang et al., Nature 403, 59 (2000)