Phase Diagram of Vortices in High-Tc Superconductors from Lattice Defect Model with Pinning

TL;DR

This paper develops a theoretical phase diagram for vortices in high-temperature superconductors, incorporating lattice defects and pinning effects, revealing complex transition lines including first-order and glass transitions.

Contribution

It introduces a comprehensive model combining elasticity, plasticity, and disorder to analyze vortex phases, extending previous quadratic approximations with a variational approach for more accurate phase boundaries.

Findings

Identifies a first-order Bragg-glass to vortex-liquid transition with reentrant behavior.

Establishes a third-order glass transition line separating vortex glass and vortex liquid.

Calculates entropy and magnetic induction jumps across the first-order transition.

Abstract

The theory presented is based on a simple Hamiltonian for a vortex lattice in a weak impurity background which includes linear elasticity and plasticity, the latter in the form of integer valued fields accounting for defects. Within a quadratic approximation in the impurity potential, we find a first-order Bragg-glass, vortex-glass transition line showing a reentrant behavior for superconductors with a melting line near $ H_{c2} $. Going beyond the quadratic approximation by using the variational approach of M\'ezard and Parisi established for random manifolds, we obtain a phase diagram containing a third-order glass transition line. The glass transition line separates the vortex glass and the vortex liquid. Furthermore, we find a unified first-order line consisting of the melting transition between the Bragg glass and the vortex liquid phase as well as a disorder induced first-order line between the Bragg glass and the vortex glass phase. The reentrant behavior of this line within the quadratic approach mentioned above vanished. We calculate the entropy and magnetic induction jumps over the first-order line.