V. Kozhevnikov

Surface enhancement of superconductivity in tin

The possibility of surface enhancement of superconductivity is examined experimentally. It is shown that single crystal tin samples with cold-worked surfaces represent a superconductor with a surface-enhanced order parameter (or negative surface extrapolation length b), whose magnitude can be controlled.

Observation of wetting-like phase transitions in a surface-enhanced type-I superconductor

Superconductivity in single crystal Sn samples with surface-enhanced order parameter is studied experimentally. Controllable surface enhancement is achieved by mechanical polishing or by ion irradiation. A first-order surface superconductivity transition is found in parallel magnetic fields close to the bulk critical field Hc(T) and for temperatures above 0.8Tc up till a surface critical temperature Tcs > Tc, where Tc is the bulk critical temperature. The resulting phase diagram agrees with that predicted for interface-delocalization or wetting transitions in type-I superconductors, based on the Ginzburg–Landau theory.