Regensburg 2010 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 31: Poster I: Devices, Quantum Dots and Quantum Wires

HL 31.29: Poster

Tuesday, March 23, 2010, 18:30–20:30, Poster D1

Wave Packet Propagation and Transport Phenomena in Multi-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 introduce a time dependent approach to describe stationary transport in multi-terminal semiconductor nanostructures. The Landauer-Büttiker formalism relates current voltage-characteristics to transmission amplitudes. Using wave packet propagation the scattering matrix can be computed efficiently for a large energy range (up to 27000 transmission amplitudes with a single wavepacket run), even for complicated potential geometries.

The investigated time dependent approach enables the simulation of recent experiments on 4-terminal Aharonov-Bohm (AB) rings etched in GaAs/AlGaAs semiconductors. The phase of the AB oscillation shows a strong dependency on the Fermi energy. Even though the phase should be continuously adjustable in a four terminal setup, strong phase rigidity prevails in the local setup. In order to explain this behavior one has to go beyond simplified 1D models and the 2D scattering potential has to be modeled realistically. This requires to include depletion effects as well as rounded lead-ring junctions. Under these conditions, the experimentally observed phase change can be reproduced within the Landauer-Büttiker framework. Finite temperature and finite bias voltage does break symmetry in the local setup and the phase rigidity is slightly lifted.