International Journal of Modern Physics B Vol. 23, No. 20 & 21 (2009) 4257–4268 c  World Scientific Publishing Company SUPERCONDUCTING NANOWIRES: QUANTUM-CONFINEMENT EFFECT ON THE CRITICAL MAGNETIC FIELD AND SUPERCURRENT M. D. CROITORU EMAT, Departement Fysica, Universiteit Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen, Belgium mihail.croitoru@ua.ac.be A. A. SHANENKO CMT, Departement Fysica, Universiteit Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen, Belgium arkady.shanenko@ua.ac.be F. M. PEETERS CMT, Departement Fysica, Universiteit Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen, Belgium francois.peeters@ua.ac.be Received 24 July 2009 We study the effect of electron confinement on the superconducting-to-normal phase transition driven by a magnetic field and/or on the current-carrying state of the su- perconducting condensate in nanowires. Our investigation is based on a self-consistent numerical solution of the Bogoliubov-de Gennes equations. We show that in a parallel magnetic field and/or in the presence of supercurrent the transition from superconduct- ing to normal phase occurs as a cascade of discontinuous jumps in the superconducting order parameter for diameters D< 10 ÷ 15 nm at T = 0. The critical magnetic field exhibits quantum-size oscillations with pronounced resonant enhancements. Keywords : Quantum confinement; Bogoliubov-de Gennes equations. 1. Introduction Recent technological advances resulted in the fabrication of superconducting nanos- tructures (mostly, nanowires and films) with significantly minimized disorder, in which the electron mean free path is of the order of — or even larger than — the sample thickness, which promises important technological applications. 1,2,3,4,5,6,7,8 Such structures are in the clean limit for the transverse/confined electron motion. It means that nonmagnetic impurities can only influence the electron motion parallel to the specimen and, then, arguments similar to the Anderson theorem 9 makes it possible to expect that the longitudinal scattering of electrons on such nonmagnetic 4257 Int. J. Mod. Phys. B 2009.23:4257-4268. Downloaded from www.worldscientific.com by UNIVERSIDADE FEDERAL DE PERNAMBUCO on 07/20/15. For personal use only.