Dresden 2014 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 30: Superconductivity - Poster Session
TT 30.22: Poster
Montag, 31. März 2014, 15:00–19:00, P2
Stability of supercurrents and condensates in type I superconductors — Pavel Lipavsky4, •Klaus Morawetz1,2,3, Bretislav Sopik5, and Michael Maennel1 — 1Münster University of Applied Sciences, Stegerwaldstrasse 39, 48565 Steinfurt, Germany — 2International Institute of Physics (IIP) Av. Odilon Gomes de Lima 1722, 59078-400 Natal, Brazil — 3Max-Planck-Institute for the Physics of Complex Systems, 01187 Dresden, Germany — 4Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, 12116 Prague 2, Czech Republic — 5Central European Institute of Technology, Masaryk University, Kamenice 735, 62500 Brno, Czech Republic
Excitations of Cooper pairs into non-condensed bound pairs are similar to excitations of true bosons out of the Bose-Einstein condensate. Using the Landau criterion of superfluidity we evaluate the critical current above which these pair-excitations would lead to a finite resistivity. The predicted value strongly depends on the chosen approximation. The Thouless approach based on the Galitskii T-matrix and the Kadanoff-Martin theory which is in many aspects equivalent to the BCS theory, both lead to zero critical velocity, what is in conflict with the mere existence of supercurrents. In contrast, the T-matrix with multiple scattering corrections provides the critical velocity of pair excitation which is p3-times larger than the critical velocity of pair breaking. This agrees with the experimentally well established fact that supercurrents in type I superconductors are limited by pair breaking, not by pair excitation