Rotational transition, domain formation, dislocations and defects in vortex systems with combined six- and 12-fold anisotropic interactions

TL;DR

This paper introduces a new vortex interaction model with combined six- and 12-fold anisotropies, revealing how vortex lattices transition, form domains, and develop defects as anisotropy ratios change, with potential applications to other anisotropic particle systems.

Contribution

The study presents a novel model for vortex interactions with combined anisotropies and explores the resulting lattice configurations, domain formations, and defect structures through numerical simulations.

Findings

Triangular vortex lattice rotates with anisotropy ratio changes.

Domain boundaries are decorated with dislocations of five- and seven-fold vortices.

Identified energy costs of various dislocations and defects.

Abstract

We introduce a new model for a pairwise repulsive interaction potential of vortices in a type-II superconductor, consisting of superimposed six- and 12-fold anisotropies. Using numerical simulations we study how the vortex lattice configuration varies as the magnitudes of the two anisotropic interaction terms change. A triangular lattice appears for all values, and rotates through 30 degrees as the ratio of the six- and 12-fold anisotropy amplitudes is varied. The transition causes the VL to split into domains that have rotated clockwise or counter-clockwise, with domain boundaries that are "decorated" by dislocations consisting of five- and seven-fold coordinated vortices. We also find intra-domain dislocations and defects, and characterize them in terms of their energy cost. We discuss how this model could be generalized to other particle-based systems with anisotropic interactions, such as colloids, and consider the limit of very large anisotropy where it is possible to create cluster crystal states.