Observation of a New Mechanism of Spontaneous Generation of Magnetic Flux in a Superconductor

TL;DR

This paper reports the discovery of a new spontaneous magnetic flux generation mechanism in superconductors, which depends on temperature gradients and differs from known theories.

Contribution

It introduces a novel flux generation mechanism linked to thermoelectric effects, challenging existing understanding of flux behavior in superconductors.

Findings

Spontaneous flux sign varies randomly between cooldowns.

Flux distribution follows a Gaussian pattern.

Width of flux distribution increases with temperature gradient.

Abstract

We report the discovery of a new mechanism of spontaneous generation of a magnetic flux in a superconductor cooled through $T_c$. The sign of the spontaneous flux changes randomly from one cooldown to the next, and follows a Gaussian distribution. The width of the distribution increases with the size of the temperature gradient in the sample. Our observations appear inconsistent with the well known mechanisms of flux generation. The dependence on the temperature gradient suggests that the flux may be generated through an instability of the thermoelectric superconducting-normal quasiparticle counterflow.