Surface impedance studies on the electrodynamical response of organic superconductors

Abstract

We have performed detailed measurements of the surface impedance in the normal a n d superconducting s t a t e of K-(BEDT-"TF)2Cu(NCS)z i n t h e millimeter wave frequency range (1 cm" to 3 cm-I), and have evaluated the complex conductivity for different crystallographic orientations. Above the transition temperature, t h e material behaves like a metal with a scattering rate of approximately 30 cm-'. In t h e superconducting s t a t e the electrodynamics of both materials is in good agreement with cdculations based on a BCS ground state: the penetration d e p t h is temperature independent for T-+ 0; while the penetration depth and the coherence length are strongly anisotrop, t h e superconducting energy g a p shows no indications of line nodes.