The phase diagram of vortex matter in layered superconductors with tilted columnar pinning centers

TL;DR

This paper maps the phase diagram of vortex matter in layered superconductors with tilted columnar defects, revealing phase transitions and the influence of defect orientation on vortex states.

Contribution

It introduces a numerical approach to study vortex phases with tilted columnar pins, highlighting differences from the normal orientation case.

Findings

Identification of Bose glass and Bragg glass phases

First order transition between Bose glass and Bragg glass

Quantitative differences from normal columnar pin configurations

Abstract

We study the vortex matter phase diagram of a layered superconductor in the presence of columnar pinning defects, {\it tilted} with respect to the normal to the layers. We use numerical minimization of the free energy written as a functional of the time averaged vortex density of the Ramakrishnan-Yussouff form, supplemented by the appropriate pinning potential. We study the case where the pin density is smaller than the areal vortex density. At lower pin concentrations, we find, for temperatures of the order of the melting temperature of the unpinned lattice, a Bose glass type phase which at lower temperatures converts, via a first order transition, to a Bragg glass, while, at higher temperatures, it crosses over to an interstitial liquid. At somewhat higher concentrations, no transition to a Bragg glass is found even at the lowest temperatures studied. While qualitatively the behavior we find is similar to that obtained using the same procedures for columnar pins normal to the layers, there are important and observable quantitative differences, which we discuss.