Driven Superconducting Vortex Dynamics in Systems with Two-Fold Anisotropy in the Presence of Pinning

TL;DR

This study investigates how two-fold anisotropic interactions influence vortex dynamics in superconductors with pinning, revealing anisotropy-dependent ordering, defect formation, and hysteresis effects during driven vortex motion.

Contribution

It provides new insights into anisotropic vortex behavior, showing how drive direction and anisotropy strength affect vortex ordering and phase transitions.

Findings

Maximum topological defects near depinning

Transition from nematic to smectic phases with drive

Hysteresis in vortex chain formation

Abstract

We examine the dynamics of superconducting vortices with two-fold anisotropic interaction potentials driven over random pinning and compare the behavior under drives applied parallel and perpendicular to the anisotropy direction. The number of topological defects reaches a maximum near depinning and then drops with increasing driving force as the vortices form one-dimensional chains. This coincides with a transition from a pinned nematic to a moving smectic aligned with the soft direction of the anisotropy. The system is generally more ordered when the drive is applied along the soft direction of the anisotropy, while for driving along the hard direction, there is a critical value of the anisotropy above which the system remains aligned with the soft direction. We also observe hysteresis in the dynamics, with one-dimensional aligned chains persisting during a decreasing drive sweep to drives below the threshold for chain formation during the increasing drive sweep. More anisotropic systems have a greater amount of structural disorder in the moving state. For lower anisotropy, the system forms a moving smectic-A state, while at higher anisotropy, a moving nematic state appears instead.