Anomalous behaviour of the in-plane electrical conductivity of the layered superconductor κ-(BEDT-TTF)_2Cu(NCS)_2
John Singleton, Charles Mielke, William Hayes, John Schlueter
Abstract
The quasiparticle scattering rates in high-quality crystals of the quasi-two-dimensional superconductor \kappa-(BEDT-TTF)_2Cu(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).