Regensburg 2010 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 46: Quantum Dots and Wires: Transport

HL 46.14: Vortrag

Mittwoch, 24. März 2010, 17:30–17:45, H17

Phase Behavior of Aharonov-Bohm Oscillations in Four-Terminal Nanodevices — •Christoph Kreisbeck¹ and Tobias Kramer^1,2 — ¹Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany — ²Department of Physics, Harvard University, Cambridge, MA 02138, USA

We discuss recent experiments on four terminal Aharonov-Bohm rings, based on GaAs/AlGaAs heterostructures. The phase of the AB oscillation shows a rich structure with variation of the top gate voltage. Even though the phase should be continuously adjustable in a four terminal setup, strong phase rigidity prevails in the local setup.

To explain this behavior within the Landauer-Büttiker formalism requires to go beyond simplified 1D-models and the scattering matrix in a realistic 2D-setup has to be computed. Provided that we include depletion effects and rounded crossings, we reproduce the experimental observed phase changes and explain the underlying mechanism. As a consequence the phase behavior fundamentally relies on the device geometry. Finite temperature and finite bias voltage does break symmetry in the local setup and the phase rigidity is slightly lifted. We computed the scattering matrix by an efficient time-dependent approach, based on wave packet propagation. Hence, simulation of complicated 4-terminal geometries for a large range of gate voltages have become accessible for the first time.