Flux quanta driven by high-density currents in low-impurity V3Si and LuNi2B2C: free flux flow and flux-core size effect

TL;DR

This study investigates how high-density currents induce flux quanta in low-impurity superconductors V3Si and LuNi2B2C, revealing the influence of flux-core size on flux flow resistivity and demonstrating a free flux flow state.

Contribution

It provides experimental evidence of flux-core size effects on flux flow resistivity and demonstrates the realization of free flux flow in high-quality superconductors under high currents.

Findings

Flux flow resistivity depends on magnetic field via flux-core size.

High currents lead to saturation of flux-flow dissipation below normal resistance.

Flux-core size decrease at higher fields aligns with BCS s-wave model predictions.

Abstract

High density direct currents (DC) are used to drive flux quanta via the Lorentz force towards a highly ordered "free flux flow" (FFF) dynamic state, made possible by the weak-pinning environment of high-quality, single-crystal samples of two low-Tc superconducting compounds, V3Si and LuNi2B2C. We report the effect of the magnetic field-dependent fluxon core size on flux flow resistivity rho_f. Much progress has been made in minimizing the technical challenges associated with the use of high currents. Attainment of a FFF phase is indicated by the saturation at highest currents of flux-flow dissipation levels that are well below the normal state resistance and have field-dependent values. The field dependence of the corresponding rho_f is shown to be consistent with a prediction based on a model for the decrease of flux core size at higher fields in weak-coupling BCS s-wave materials.