Critical Behavior of the Flux-line Tension in Extreme Type-II Superconductors

TL;DR

This paper investigates the critical behavior of flux-line tension in extreme type-II superconductors, revealing how entropic effects influence the lower-critical field near the transition, with implications for high-temperature superconductors.

Contribution

It introduces a schematic dual Villain model to compute entropic corrections to flux-line energy and analyzes the temperature dependence of the lower-critical field in different superconductor configurations.

Findings

Lower-critical field vanishes polynomially with an exponent ~2/3 in isotropic case

Inflection point observed in layered superconductor configurations

Experimental hints of these effects in high-temperature superconductors

Abstract

The entropic corrections to the flux-line energy of extreme type-II superconductors are computed using a schematic dual Villain model description of the flux quanta. We find that the temperature profile of the lower-critical field vanishes polynomially at the transition with an exponent $\nu\cong 2/3$ in the isotropic case, while it exhibits an inflection point for the case of weakly coupled layers in parallel magnetic field. It is argued that vestiges of these effects have already been observed in high-temperature superconductors.