Nonlocal vs local vortex dynamics in the transversal flux transformer effect

TL;DR

This paper investigates the superconducting transversal flux transformer effect (TFTE) in amorphous NbGe nanostructures, revealing its relation to local vortex dynamics and how it varies from electron heating at low T to the Larkin-Ovchinnikov effect near Tc.

Contribution

It demonstrates that TFTE can reliably determine microscopic vortex mechanisms and traces the evolution from electron heating to the Larkin-Ovchinnikov effect across a wide temperature range.

Findings

TFTE correlates with local vortex dynamics.

Electron heating dominates at low T.

Larkin-Ovchinnikov effect appears near Tc.

Abstract

In this follow-up to our recent Letter [F. Otto et al., Phys. Rev. Lett. 104, 027005 (2010)], we present a more detailed account of the superconducting transversal flux transformer effect (TFTE) in amorphous (a-)NbGe nanostructures in the regime of strong nonequilibrium in local vortex motion. Emphasis is put on the relation between the TFTE and local vortex dynamics, as the former turns out to be a reliable tool for determining the microscopic mechanisms behind the latter. By this method, a progression from electron heating at low temperatures T to the Larkin-Ovchinnikov effect close to the transition temperature Tc is traced over a range 0.26 < T/Tc < 0.95. This is represented by a number of relevant parameters such as the vortex transport entropy related to the Nernst-like effect at low T, and a nonequilibrium magnetization enhancement close to Tc. At intermediate T, the Larkin-Ovchinnikov effect is at high currents modified by electron heating, which is clearly observed only in the TFTE.