Berlin 2005 – scientific programme
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HL: Halbleiterphysik
HL 45: Quantenpunkte und -dr
ähte: Transporteigenschaften II
HL 45.7: Talk
Monday, March 7, 2005, 16:30–16:45, TU P-N202
Conductance anomalies in nonlinear transport through a quantum point contact — •M. Fleischer1, D.J. Schefzyk1, D.A. Wharam1, D.A. Ritchie2, and M. Pepper2 — 1Institut für Angewandte Physik, Universität Tübingen, Auf der Morgenstelle 10, D-72076 Tübingen — 2Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE, UK
Transport measurements of quantum point-contacts lead to the well-known conductance quantisation in units of G0 = 2e2/h. We have investigated point-contacts defined in the two-dimensional electron gas of a GaAs/AlGaAs heterostructure. The differential conductance exhibits plateaux at the expected integer multiples of G0 and their half-integer counterparts at finite bias. In addition, there is a distinct step below the first plateau, widely known as the No-dq0.7-structureNo-dq, as well as a corresponding step below the second plateau, at about 1.6 G0. At finite bias, both additional steps first develop into plateaux at about 0.8 G0 and 1.5 G0 respectively, then into side plateaux at intermediate values in analogy to the integer/half-integer structure, leading to a pattern of intersecting diamonds in the transconductance. The possible origin of extra steps has been considered in a numerical calculation of one-dimensional subbands.