Softening and melting of a vortex lattice in presence of point disorder

TL;DR

This paper presents a phenomenological model for vortex lattice melting, highlighting how dislocation screening leads to softening, a transition to hexatic phases, and complex vortex dynamics, supported by experimental observations.

Contribution

It introduces a new model linking dislocation screening to vortex lattice melting and predicts a continuous transition to a glassy phase in 3D vortex systems.

Findings

Identification of a first-order softening line ending at a critical point.

Prediction of a crossover to an hexatic vortex solid.

Observation of reentrant vortex behavior and non-monotonous creep exponents.

Abstract

A phenomenological model is proposed for melting of a vortex lattice, based on screening of the elastic shear modulus by mobile or partially pinned dislocations. A first-order softening line is found and ends at a critical point beyond which the lattice crosses over to an hexatic vortex solid. The consequences of softening on vortex dynamics are explored, as fingerprints of plastic dynamics: a reentrance of single vortex behaviour, for both depinning and collective creep, occurs as the field increases, with non-monotonous creep exponents. This general scenario is supported by recent experiments in high-$T_c$ materials and suggests that for a 3D vortex lattice at low temperature the field induces a continuous order-disorder transition towards a glassy phase.