CRITICAL-BEHAVIOR OF THE FLUX-LINE TENSION IN EXTREME TYPE-II SUPERCONDUCTORS

The entropic corrections to the flux-line energy of extreme type-II su perconductors are computed using a schematic dual Villain model descri ption of the flux quanta. We find that the temperature profile of the lower critical field vanishes polynomially at the transition with an e xponent nu congruent to 2/3 in the isotropic case, while it exhibits a n inflection point for the case of weakly coupled layers in parallel m agnetic field. It is argued that vestiges of these effects have alread y been observed in high-temperature superconductors.