Anomalous behaviour of the in-plane electrical conductivity of the layered superconductor $\kappa$-(BEDT-TTF)$_2$Cu(NCS)$_2$

TL;DR

This study investigates the quasiparticle scattering rates in a layered superconductor, revealing that in-plane electrical conductivity exhibits anomalous behavior inconsistent with Fermi-liquid theory, due to spatial inhomogeneities.

Contribution

The paper provides new insights into quasiparticle scattering mechanisms in $ppa$-(BEDT-TTF)$_2$Cu(NCS)$_2$, highlighting the role of spatial inhomogeneities and challenging existing theoretical predictions.

Findings

Landau-level broadening caused mainly by spatial inhomogeneities

Quasiparticle lifetime for Landau states exceeds 3 ps

Intralayer scattering time is significantly shorter than Fermi-liquid predictions

Abstract

The quasiparticle scattering rates in high-quality crystals of the quasi-two-dimensional superconductor $\kappa$-(BEDT-TTF)$_2$Cu(NCS)$_2$ ~are studied using the Shubnikov-de Haas effect and MHz penetration-depth experiments. There is strong evidence that the broadening of the Landau-levels is primarily caused by spatial inhomogeneities, indicating a quasiparticle lifetime for the Landau states $\gg 3$ ps. In contrast to the predictions of Fermi-liquid theory, the scattering time derived from the intralayer conductivity is found to be much shorter ($0.14-0.56$ ps).