Flux-lattice melting in two-dimensional disordered superconductors

TL;DR

This study uses Monte Carlo simulations to analyze flux lattice melting in two-dimensional superconductors, revealing how disorder affects the transition and the nature of vortex order.

Contribution

It provides new insights into the effects of disorder on vortex lattice melting and the nature of vortex glass phases in two-dimensional superconductors.

Findings

Disorder shifts the melting line to lower fields.

Vortex positional correlations decay as a power law, indicating a quasi-long range ordered positional glass.

Phase coherence in vortex glass decays exponentially, ruling out a phase coherent vortex glass.

Abstract

The flux line lattice melting transition in two-dimensional pure and disordered superconductors is studied by a Monte Carlo simulation using the lowest Landau level approximation and quasi-periodic boundary condition on a plane. The position of the melting line was determined from the diffraction pattern of the superconducting order parameter. In the clean case we confirmed the results from earlier studies which show the existence of a quasi-long range ordered vortex lattice at low temperatures. Adding frozen disorder to the system the melting transition line is shifted to slightly lower fields. The correlations of the order parameter for translational long range order of the vortex positions seem to decay slightly faster than a power law (in agreement with the theory of Carpentier and Le Doussal) although a simple power law decay cannot be excluded. The corresponding positional glass correlation function decays as a power law establishing the existence of a quasi-long range ordered positional glass formed by the vortices. The correlation function characterizing a phase coherent vortex glass decays however exponentially ruling out the possible existence of a phase coherent vortex glass phase.