Equipartition of Current in Parallel Conductors on Cooling Through the Superconducting Transition

TL;DR

This paper demonstrates that in parallel superconducting wires of different lengths, the current naturally redistributes to equal values as the temperature approaches the superconducting transition, due to flux-flow resistance effects.

Contribution

It reveals a spontaneous current equipartition phenomenon in parallel superconductors driven by flux-flow resistance near the transition temperature.

Findings

Current ratios approach unity at Tc.

Current distribution remains stable below Tc.

Flux-flow resistance causes the redistribution.

Abstract

Our experiments show that for two or more pieces of a wire, of different lengths in general, combined in parallel and connected to a dc source, the current ratio evolves towards unity as the combination is cooled to the superconducting transition temperature Tc, and remains pinned at that value below it. This re-distribution of the total current towards equipartition without external fine tuning is a surprise. It can be physically understood in terms of a mechanism that involves the flux-flow resistance associated with the transport current in a wire of type-II superconducting material. It is the fact that the flux-flow resistance increases with current that drives the current division towards equipartition.