Domain regime in two-dimensional disordered vortex matter

TL;DR

This study uses numerical simulations to explore how vortices in disordered 2D superconductors organize into different regimes, identifying a distinct domain regime with quasi-ordered structures and analyzing the transition mechanisms between regimes.

Contribution

It introduces the concept of the domain regime in disordered vortex matter and characterizes its properties and transition mechanisms through detailed numerical analysis.

Findings

Identification of the domain regime with quasi-ordered vortex structures.

Observation of a crossover from domain regime to amorphous high-field regime.

Analysis of domain wall roughening as a transition mechanism.

Abstract

A detailed numerical study of the real space configuration of vortices in disordered superconductors using 2D London-Langevin model is presented. The magnetic field $B$ is varied between 0 and $B_{c2}$ for various pinning strengths $\Delta$. For weak pinning, an inhomogeneous disordered vortex matter is observed, in which the topologically ordered vortex lattice survives in large domains. The majority of the dislocations in this state are confined to the grain boundaries/domain walls. Such quasi-ordered configurations are observed in the intermediate fields, and we refer it as the domain regime (DR). The DR is distinct from the low-field and the high-fields amorphous regimes which are characterized by a homogeneous distribution of defects over the entire system. Analysis of the real space configuration suggests domain wall roughening as a possible mechanism for the crossover from the DR to the high-field amorphous regime. The DR also shows a sharp crossover to the high temperature vortex liquid phase. The domain size distribution and the roughness exponent of the lattice in the DR are also calculated. The results are compared with some of the recent Bitter decoration experiments.