Results for the phase diagram of the vortex system in two-dimensional superconductors

V. N. Ryzhov; E. E. Tareyeva

doi:10.1103/PhysRevB.49.6162

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Results for the phase diagram of the vortex system in two-dimensional superconductors

V. N. Ryzhov, E. E. Tareyeva

DOI 10.1103/PhysRevB.49.6162 · Physical Review B

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Abstract

The thermodynamics of a two-dimensional vortex plasma in thin-film superconductors is described in the framework of a cycle approximation. The equations for density of free vortices are obtained from the virial expansion. These equations provide a unified approach to describe both the Kosterlitz-Thouless-like behavior in the vicinity of the characteristic transition temperature TKT (smooth, but very rapid crossover from the state with lower free vortex density to the state with larger vortex density) and the resistive tail at low temperatures. It is shown that in an applied magnetic field H0 the discontinuous vortex-unbinding transition occurs before the Kosterlitz-Thouless-like transition when an external field exceeds some critical value. The dependence of the Kosterlitz-Thouless-like transition on the vortex core radius r0 connected to the vortex core energy is discussed. It is suggested that for r0 less than some critical value r0c there is the discontinuous vortex-unbinding transition while for r0>r0c the transition has the usual Kosterlitz-Thouless-like form.