Stiffness and coherence length measurements of ultra-thin superconductors, and implications for layered superconductors

Based on the London equation, we use a rotor-free vector potential A and current measurements by a SQUID, to determine the superconducting (SC) Pearl length Λ and coherence length ζ 0, of ultra-thin, ring shaped, MoSi films, as a function of thickness d and temperature T. We find that T c and ζ 0 are functions of d and both jump at ζ0∼d∼5 nm. At base temperature the SC stiffness, defined by 1/λ2=1/(Λd), is an increasing function of T c . Similar behavior, known as the Uemura plot, exists in bulk layered superconductors, but with doping as an implicit parameter. We also provide the critical exponents of Λ(T) .