Dresden 2009 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 32: Postersession Superconductivity: Josephson Junctions, SQUIDs, Heterostructures, Andreev Scattering, Vortex Physics, Cryodetectors, Measuring Devices, Cryotechnique
TT 32.20: Poster
Wednesday, March 25, 2009, 14:00–18:00, P1A
Decreasing excitation gap in Andreev billiards by disorder scattering — •Florian Libisch1, Jürgen Möller1, Stefan Rotter1, Maxim Vavilov2, and Joachim Burgdörfer1 — 1TU--Vienna, Austria — 2University of Wisconsin, USA
We investigate the distribution of the lowest-lying energy states in a disordered Andreev billiard by solving the Bogoliubov-de Gennes equation numerically [1]. Contrary to conventional predictions we find a decrease rather than an increase of the excitation gap relative to its clean ballistic limit. We relate this finding to the eigenvalue spectrum of the Wigner-Smith time delay matrix between successive Andreev reflections. We show that the longest rather than the mean time delay determines the size of the excitation gap. With increasing disorder strength the values of the longest delay times increase, thereby, in turn, reducing the excitation gap.
[1] F. Libisch, J. Möller, S. Rotter, M. G. Vavilov, J. Burgdörfer, Europhys. Lett. 82, 47006 (2008).