Plastic Motion of a Flux-line Lattice Driven by Alternating Current

TL;DR

This study investigates the dynamic behavior of flux-line lattices in a superconductor under alternating currents, revealing novel non-linear responses and memory effects linked to structural changes.

Contribution

It demonstrates the existence of unique flux-line responses to specific alternating current protocols, highlighting new non-linear phenomena and memory effects in flux lattices.

Findings

Flux-lines respond to reversed currents at low amplitudes.

Memory effects suggest dynamic structural changes.

Distinct responses depend on current switching protocols.

Abstract

We have measured the response of the flux-line lattice in the low T$_c$ superconductor, 2H-NbSe$_2$, to finite frequency drives. In a well-defined range of fields, temperatures, and driving amplitudes the system exhibits a variety of novel non-linear phenomena. Most strikingly, the flux-lines can move easily in response to currents that are significantly lower than the DC critical current if the direction of the current is reversed periodically while the amplitude, I, is kept fixed, but they do not respond to a current that periodically switches between zero and I, while the direction is kept fixed. Pronounced memory effects associated with these phenomena indicate the presence of dynamically generated structural changes in the flux lattice.