Berlin 2005 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 58: Poster IIb

HL 58.5: Poster

Dienstag, 8. März 2005, 16:30–19:00, Poster TU F

Conductance anomalies in a quantum point contact — •D.J. Schefzyk1, M. Fleischer1, S. Jauerneck1, D.A. Wharam1, D.A. Ritchie2, and M. Pepper21Institut 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 exhibit conductance quantisation in units of G0 = 2e2/h. Often additional steps are observed which cannot be accounted for in the simple picture of perfectly transmitting one-dimensional subbands. In the linear gate characteristics, the observed transconductance structure moves parabolically towards lower absolute values of gate voltage with increased perpendicular magnetic field. In addition, we see distinct side plateaux at finite magnetic field. The zero field differential conductance in the nonlinear regime exhibits plateaux at integer multiples of G0 and half-integer plateaux at finite bias as well as distinct steps below the first and second plateau. At finite bias, they develop into side plateaux, leading to a pattern of intersecting diamonds in the transconductance. The possible origin of additional steps has been considered in a numerical calculation of one-dimensional subbands.

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