Reversible Vortex Ratchet Effects and Ordering in Superconductors with Simple Asymmetric Potential Arrays

TL;DR

This study uses simulations to show that simple asymmetric 1D potential arrays in superconductors can produce vortex ratchet effects with multiple reversals, depending on vortex density and lattice structure, revealing complex vortex dynamics.

Contribution

It demonstrates that a simple 1D asymmetric potential array can replicate complex vortex ratchet behaviors seen in more complicated systems, including reversals and lattice-dependent effects.

Findings

Ratchet effect sign reverses with vortex density and substrate strength

Ordered vortex lattices produce standard ratchet responses

Disordered phases lead to ratchet sign reversals and diode effects

Abstract

We demonstrate using computer simulations that the simplest vortex ratchet system for type-II superconductors with artificial pinning arrays, an asymmetric one-dimensional (1D) potential array, exhibits the same features as more complicated two-dimensional vortex ratchets that have been studied in recent experiments. We show that the 1D geometry, originally proposed by Lee et al. [Nature 400, 337 (1999)], undergoes multiple reversals in the sign of the ratchet effect as a function of vortex density, substrate strength, and ac drive amplitude, and that the sign of the ratchet effect is related to the type of vortex lattice structure present. When the vortex lattice is highly ordered, an ordinary vortex ratchet effect occurs which is similar to the response of an isolated particle in the same ratchet geometry. In regimes where the vortices form a smectic or disordered phase, the vortex-vortex interactions are relevant and we show with force balance arguments that the ratchet effect can reverse in sign. The dc response of this system features a reversible diode effect and a variety of vortex states including triangular, smectic, disordered and square.