Dissipation in the superconducting state of kappa-(BEDT-TTF)2Cu(NCS)2

TL;DR

This study investigates the interlayer resistivity of a quasi-two-dimensional organic superconductor, revealing a non-zero resistivity region influenced by magnetic field and current, explained by vortex dynamics and phase slips.

Contribution

It provides a detailed analysis of resistivity behavior in the superconducting state, introducing a model based on phase slips and vortex motion specific to this material.

Findings

Identification of a non-zero resistivity region in the superconducting state.

Correlation of resistivity behavior with vortex solid-liquid transition.

Proposal of a phase slip model involving pancake vortices.

Abstract

We have studied the interlayer resistivity of the prototypical quasi-two-dimensional organic superconductor $\kappa$-(BEDT-TTF)$_2$Cu(NCS)$_2$ as a function of temperature, current and magnetic field, within the superconducting state. We find a region of non-zero resistivity whose properties are strongly dependent on magnetic field and current density. There is a crossover to non-Ohmic conduction below a temperature that coincides with the 2D vortex solid -- vortex liquid transition. We interpret the behaviour in terms of a model of current- and thermally-driven phase slips caused by the diffusive motion of the pancake vortices which are weakly-coupled in adjacent layers, giving rise to a finite interlayer resistance.