Guiding of vortices and ratchet effect in superconducting films with asymmetric pinning potential

TL;DR

This paper models vortex dynamics in superconducting films with asymmetric pinning, deriving new nonlinear voltages influenced by vortex guiding and ratchet asymmetry, revealing their behavior near resistive transitions.

Contribution

It introduces explicit formulas for nonlinear anisotropic voltages in vortex motion considering thermal fluctuations and asymmetric pinning potentials.

Findings

Derived explicit expressions for new nonlinear voltages.

Identified the physical origin of odd voltages due to vortex guiding and asymmetry.

Showed voltages vanish in linear regimes and peak near nonlinear resistive transitions.

Abstract

Two-dimensional vortex dynamics in a ratchet washboard planar pinning potential (PPP) in the presence of thermal fluctuations is considered on the basis of a Fokker-Planck equation. Explicit expressions for two new nonlinear anisotropic voltages (longitudinal and transverse with respect to the current direction) are derived and analyzed. The physical origin of these odd (with respect to magnetic field or transport current direction reversal) voltages is caused by the interplay between the even effect of vortex guiding and the ratchet asymmetry. Both new voltages are going to zero in the linear regimes of the vortex motion (i.e. in the thermally activated flux flow (TAFF) and ohmic flux flow (FF) regimes) and have a bump-like current or temperature dependence in the vicinity of the highly nonlinear resistive transition from the TAFF to the FF.