Pressure-temperature phase diagram, inverse isotope effect, and superconductivity in excess of 13 K in κ-(BEDT-TTF)2Cu[N(CN)2]Cl, where BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene

Abstract
The pressure-temperature phase diagram of the highest-Tc organic superconductor, κ-(BEDT-TTF)2Cu[N(CN)2]Cl is determined, where BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene. Semiconducting, insulating, metallic, and superconducting regimes are seen at pressures below 1 kbar. Superconductivity at 12.5 K and 0.3 kbar increases by 0.5–1.5 K upon deuteration of BEDT-TTF, in striking contrast to the normal isotope effect determined previously for κ-(BEDT-TTF)2Cu[N(CN)2]Br.