Anisotropic Vortices in High-Temperature Superconductors and the Onset of Vortex-like Excitations above the Critical Temperature

TL;DR

This paper proposes a theory explaining the presence of vortex-like excitations above the critical temperature in high-temperature superconductors, linked to a first-order phase transition to a vortex superconducting state with anisotropic vortices.

Contribution

It introduces a new theoretical framework describing a first-order phase transition and vortex-like excitations above the critical temperature in layered high-temperature superconductors.

Findings

Vortex-like excitations can occur above the critical temperature.

The transition involves a first-order phase change with overheating and overcooling effects.

Experimental signals like Nernst effect are explained by the theory.

Abstract

Recently we have found that a three-dimensional superconducting state with anisotropic vortices localized at the vortex-lattice points is a stable state in zero external magnetic field for the layered high temperature uperconductivity materials. There exists a phase transition at the temperature $T_{c}^{v}$ from the normal phase to the vortex superconducting state which is of the first order. The first order phase transition shows overheating and overcooling effects. Nucleation of the superconducting phase in the normal phase thus may occur at temperatures higher than the transition temperature $T_{c}^{v}$. Then the onset of the vortex-like excitations above the transition temperature $T_{c}^{v}$ occurs in our theory. The onset of the vortex-like excitations in Nerst signal and some other experimental evidence for these excitations above the transition temperature $T_{c}^{v}$ in LSCO, YBCO and in other high-temperature materials may be explained thus by our theory. The vortex-like excitations above and below the transition temperature $T_{c}^{v}$ in high temperature materials continuously evolve. This fact may be explained within our theory.