Structural Transitions in Vortex Systems with Anisotropic Interactions

TL;DR

This paper models vortices in type-II superconductors with anisotropic interactions, revealing how vortex lattice structures transition from triangular to square with increasing anisotropy, including complex intermediate and chain states.

Contribution

Introduces a novel model of vortex interactions with four-fold anisotropy and demonstrates structural transitions in vortex lattices through numerical simulations.

Findings

Triangular lattice at low anisotropy

Square lattice at high anisotropy

Observation of multi-q Archimedean tiling and chain states

Abstract

We introduce a model of vortices in type-II superconductors with a four-fold anisotropy in the vortex-vortex interaction potential. Using numerical simulations we show that the vortex lattice undergoes structural transitions as the anisotropy is increased, with a triangular lattice at low anisotropy, a rhombic intermediate state, and a square lattice for high anisotropy. In some cases we observe a multi-$q$ state consisting of an Archimedean tiling that combines square and triangular local ordering. At very high anisotropy, domains of vortex chain states appear. We discuss how this model can be generalized to higher order anisotropy as well as its applicability to other particle-based systems with anisotropic particle-particle interactions.