Pressure studies on a low-resistance variant of the quasi2D organic superconductor κ-(ET)₂Cu[N(CN)₂]Br

Measurements of the interlayer resistivity, ρ(T), under hydrostatic pressure have been performed on a low (LR)- and high (HR)-resistance variant of the title organic superconductor. While the HR sample, synthesized according to the standard procedure, shows a semimetallic-like ρ(T) behavior at high temperatures followed by the pronounced maximum around 90 K, the LR crystal, which is the result of a somewhat modified synthesis route, remains metallic for . Common to both variants is, however, an almost abrupt change in ρ(T) around , consistent with a density-wave-type instability, which below coexists with superconductivity, and a ρAT2 dependence for TcTT0. While T* and Tc are sample independent, the values for A and T0 were found to differ markedly between both variants, inconsistent with the T2 dependence originating from coherent Fermi-liquid excitations.