Effective forces between interfaces in type-I superconductors

Laboratorium Voor Vaste Stoffysica en Magnetisme, Katholieke Universiteit Leuven Celestijnenlaan 200D, B-3001 Leuven, Belgium and Universität Essen, Fachbereich Physik - D-45117 Essen, Germany

Received: 1 December 2000
Accepted: 1 March 2001

Abstract

Semi-infinite type-I superconductors with surface enhancement at the wall show interface delocalization transitions analogous to wetting transitions in classical liquids. Within Ginzburg-Landau theory the effective forces between the wall and the SC/N-interface decay exponentially ("short-range forces"). Going beyond GL-theory we show that in general planar interfaces of a type-I superconductor with vacuum, normal conductors or other superconductors interact via long-ranged (algebraic) dispersion forces. Invoking BCS-results for the dielectric function of a superconductor an algebraic correction to the effective interface potential of the unusual form is found, where is the thickness of the surface superconducting sheath. This in contrast to classical fluids, where the retarded contribution is . The effective force can be either attractive or repulsive depending on the superconductor used for surface enhancement. Consequences for the interface displacement transition scenario are outlined.