paper

Vortex Interactions and Thermally Induced Crossover from Type-I to Type-II Superconductivity

arXiv:cond-mat/0202215 · doi:10.1103/PhysRevB.66.064524

Abstract

We have computed the effective interaction between vortices in the Ginzburg-Landau model from large-scale Monte-Carlo simulations, taking thermal fluctuations of matter fields and gauge fields fully into account close to the critical temperature. We find a change, in the form of a crossover, from attractive to repulsive effective vortex interactions in an intermediate range of Ginzburg-Landau parameters upon increasing the temperature in the superconducting state. This corresponds to a thermally induced crossover from \typeI to \typeII superconductivity around a temperature , which we map out in the vicinity of the metal-to-superconductor transition. In order to see this crossover, it is essential to include amplitude fluctuations of the matter field, in addition to phase-fluctuations and gauge-field fluctuations. We present a simple physical picture of the crossover, and relate it to observations in \metal{Ta} and \metal{Nb} elemental superconductors which have low-temperature values of in the relevant range.

9 pages, 6 figures. Accepted for publication in Physical Review B

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