One-dimensional resistive states in quasi-two-dimensional superconductors

TL;DR

This study explores how one- and two-dimensional topological excitations influence resistive states in quasi-two-dimensional superconductors, revealing that phase slips dominate resistivity below the transition temperature, even in wider samples.

Contribution

It demonstrates that thermally activated phase slip strips primarily cause resistivity below the transition temperature in quasi-2D superconductors, challenging the expectation that vortices dominate.

Findings

Resistivity below T_{C0} is due to phase slips, not vortices.

PSS contribution dominates over vortices in a wide current/temperature range.

Quantum phase slips are only significant below extremely low resistivity levels.

Abstract

We investigate competition between one- and two-dimensional topological excitations - phase slips and vortices - in formation of resistive states in quasi-two-dimensional superconductors in a wide temperature range below the mean-field transition temperature $T_{C0}$. The widths $w$ = 100 nm of our ultrathin NbN samples is substantially larger than the Ginzburg-Landau coherence length $\xi$ = 4nm and the fluctuation resistivity above $T_{C0}$ has a two-dimensional character. However, our data shows that the resistivity below $T_{C0}$ is produced by one-dimensional excitations, - thermally activated phase slip strips (PSSs) overlapping the sample cross-section. We also determine the scaling phase diagram, which shows that even in wider samples the PSS contribution dominates over vortices in a substantial region of current/temperature variations. Measuring the resistivity within seven orders of magnitude, we find that the quantum phase slips can only be essential below this level.