Regensburg 2007 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 13: Poster 1
HL 13.53: Poster
Monday, March 26, 2007, 15:00–17:30, Poster A
Mode spectroscopy of tunnel-coupled asymmetric quantum point contacts — •S. S. Buchholz1, S. F. Fischer1, U. Kunze1, D. Schuh2 und Gerhard Abstreiter2 — 1Werkstoffe und Nanoelektronik, Ruhr-Universität Bochum — 2Walter Schottky Institut, Technische Universität München
Semiconductor electron waveguides separated by a tunneling barrier show interesting coupling phenomena based on coherent electron transport. Vertically stacked quantum point contacts (QPCs) of equal width (symmetric configuration) have recently been investigated [1], [2]. Atomic force microscope lithography and wet chemical etching [3] allow the preparation of large one-dimensional (1D) subband separations (>10 meV). Here, we present in analogy tunnel-coupled QPCs of unequal width (asymmetric configuration). A top gate voltage (Vtg) controls the occupation of 1D subbands in both QPCs, a back gate voltage (Vbg) influences the occupation of mainly the bottom QPC, and cooling under back gate voltage allows the tuning of the bottom QPC confining potential. We record the conductance and transconductance with respect to Vtg, Vbg and magnetic field, and observe a lift of subband degeneracy for modes with equal parity in high perpendicular magnetic fields (>3 T). In longitudinal magnetic fields the coupling induced energy splittings indicate an oscillatory behavior.[1] S.F. Fischer et al., Nature Physics 2, 91 (2006). [2] S.F. Fischer et al., Phys. Rev. B 74, 115324 (2006). [3] U. Kunze, Supperlatt. Microstruct. 31, 3 (2002).