Dissipation in ultra-thin current-carrying superconducting bridges; evidence for quantum tunneling of Pearl vortices

TL;DR

This study investigates dissipation mechanisms in ultra-thin superconducting bridges, providing evidence that quantum tunneling of Pearl vortices dominates low-temperature behavior, contrasting with thermal activation at higher temperatures.

Contribution

It presents experimental evidence for quantum tunneling of Pearl vortices in high-$T_c$ superconducting bridges, expanding understanding of vortex dynamics at low temperatures.

Findings

Power-law voltage-current relationship at high T and currents

Exponential temperature dependence of resistance at high T

Logarithmic voltage dependence at low T indicating quantum tunneling

Abstract

We have made current-voltage (IV) measurements of artificially layered high-$T_c$ thin-film bridges. Scanning SQUID microscopy of these films provides values for the Pearl lengths $\Lambda$ that exceed the bridge width, and shows that the current distributions are uniform across the bridges. At high temperatures and high currents the voltages follow the power law $V \propto I^n$, with $n=\Phi_0^2/8\pi^2\Lambda k_B T+1$, and at high temperatures and low-currents the resistance is exponential in temperature, in good agreement with the predictions for thermally activated vortex motion. At low temperatures, the IV's are better fit by $\ln V$ linear in $I^{-2}$. This is expected if the low temperature dissipation is dominated by quantum tunneling of Pearl vortices.