Flux-flow instability across Berezinskii Kosterlitz Thouless phase transition in KTaO$_3$ (111) based superconductor

TL;DR

This study investigates energy dissipation mechanisms in a 2D superconductor across the BKT transition, revealing hot-spots, flux-flow instability, and hysteresis effects at high currents, advancing understanding of superconductor-to-normal state transition.

Contribution

It uncovers flux-flow instability and hysteresis phenomena in a 2D superconductor across the BKT transition at high currents, which were previously unexplored.

Findings

Hot-spots and flux-flow instability dominate dissipation below T_BKT.

Flux-flow instability causes voltage hysteresis between T_BKT and T_C.

High-current dissipation mechanisms differ from low-current behavior.

Abstract

The nature of energy dissipation in 2D superconductors under perpendicular magnetic field at small current excitations has been extensively studied over the past two decades. However, dissipation mechanisms at high current drives remain largely unexplored. Here we report on the distinct behavior of energy dissipation in the AlOx/KTaO$_3$ (111) system hosting 2D superconductivity in the intermediate disorder regime. The results show that below the Berezinskii Kosterlitz Thouless (BKT) phase transition temperature ($T_\mathrm{BKT}$), hot-spots and Larkin Ovchinnikov type flux-flow instability (FFI) are the major channels of dissipation, leading to pronounced voltage instability at large currents. Furthermore, such FFI leads to a rare observation of clockwise hysteresis in current-voltage characteristics within the temperature range $T_\mathrm{BKT} < T < T_\mathrm{C}$ ($T_\mathrm{C}$ is superconducting transition temperature). These findings deepen our understanding of how a BKT system ultimately transforms to a normal state under increasing current.