Fluctuating Superconductivity in the Strongly Correlated Organic Superconductor κ-(BEDT-TTF)₂Cu[N(CN)₂]Br

Abstract

We report the magnetoresistance and magnetic torque measurements for a highly correlated two-dimensional organic superconductor κ-(BEDT-TTF)2Cu[N(CN)2]Br (κ-Br), which has an effectively larger electron correlation than the isostructural superconductor κ-(BEDT-TTF)2Cu(NCS)2 (κ-NCS). In a magnetic field applied parallel to the conducting layers, we found that the fluctuating superconductivity (FSC) appears in a wide temperature and field range, in which the magnetic torque shows diamagnetism whereas the resistance shows no appreciable reduction in value. The FSC phase diagram of κ-Br is similar to that of κ-NCS, which is inconsistent with previous Nernst measurements.