Bragg-Bose glass phase in vortex states of high-$T_{\rm c}$ superconductors with sparse and weak columnar defects

TL;DR

This study uses large-scale simulations to reveal a new Bragg-Bose glass phase in vortex states of high-$T_c$ superconductors with sparse, weak columnar defects, showing complex phase transitions and vortex behaviors.

Contribution

First numerical observation of the Bragg-Bose glass phase in vortex states with sparse, weak columnar defects in high-$T_c$ superconductors.

Findings

Identification of the Bragg-Bose glass phase with hexagonal Bragg spots.

Increase in melting temperature with defect density due to 'selected pinning'.

Transition from Bragg-Bose glass to Bose glass as defect density increases.

Abstract

Phase diagram of vortex states of high-$T_{\rm c}$ superconductors with {\it sparse and weak} columnar defects is obtained by large-scale Monte Carlo simulations of the three-dimensional anisotropic, frustrated XY model. The Bragg-Bose glass phase characterized by hexagonal Bragg spots and the diverging tilt modulus is observed numerically for the first time at low density of columnar defects. As the density of defects increases, the melting temperature increases owing to "selected pinning" of flux lines. When the density of defects further increases, the transition to the Bose glass phase occurs. The interstitial liquid region is observed between these two glass phases and the vortex liquid phase.