Eur. Phys. J. B (2014) 87: 8
https://doi.org/10.1140/epjb/e2013-40932-2

Regular Article

Stability of supercurrents and condensates in type I superconductors

¹ Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, 12116 Prague 2, Czech Republic
² Münster University of Applied Sciences, Stegerwaldstrasse 39, 48565 Steinfurt, Germany
³ International Institute of Physics (IIP), Av. Odilon Gomes de Lima 1722, 59078-400 Natal, Brazil
⁴ Max-Planck-Institute for the Physics of Complex Systems, 01187 Dresden, Germany
⁵ Central European Institute of Technology, Masaryk University, Kamenice 735, 62500 Brno, Czech Republic

^a e-mail: morawetz@fh-muenster.de

Received: 18 October 2013
Received in final form: 26 November 2013
Published online: 13 January 2014

Abstract

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 √3-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.