Dresden 2009 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 17: Quantum wires: Optical and transport properties

HL 17.7: Vortrag

Dienstag, 24. März 2009, 11:45–12:00, BEY 154

Magnetic barriers in quantum wires — •Mihai Cerchez¹, Hengyi Xu¹, Alexey Tarasov¹, Thomas Heinzel¹, Stefan Hugger², Igor Zozoulenko³, Dirk Reuter⁴, and Andreas Wieck⁴ — ¹Heinrich-Heine-Universität, Düsseldorf, Germany — ²Fraunhofer Institut für Angewandte Festkörperphysik, Freiburg, Germany — ³Linköping University, Norrköping, Sweden — ⁴Ruhr-Universität Bochum, Bochum, Germany

A strongly localized, spatially varying magnetic field (magnetic barrier, MB) is created by the stray field at the edge of a magnetised ferromagnetic material aligned across a quantum wire (QWR). The quantum wire is produced by local anodic oxidation of a GaAs/AlGaAs heterostructure with a two-dimensional electron gas below the surface. We find pronounced and reproducible conductance fluctuations of the QWR as a function of the MB height tuned by the field applied, for various values of the electronic wire width tuned by the in-plane gates. The conductance fluctuations are strongly temperature dependent but visible up to 10 K. The findings differ both from what is expected from larger size samples and from homogenous magnetic fields. Our analysis supported by simulations using the recursive Green's functions technique shows that the observed effects are caused by the coherent part of the electron wave function which, by scattering in the impurity potential landscape creates an interference pattern depending on the position of the scatterers and the height of the MB. The MB acts like a repulsive scatterer which can be tuned to form a resonator inside the QWR.