Near constancy of the pressure dependence of across families of organic and fullerene superconductors

Pressure strongly depresses the superconducting transition temperature (Formula presented) of both the doped fullerenes and the β-ET[(BEDT-TTF(Formula presented), (BEDT-TTF)=bis(ethylenedithio)tetrathiofulvalene)] organic superconductors. An outstanding puzzle in these materials is the weak variation (Formula presented)/dP across families of compounds with large variations in (Formula presented). This property has been used to argue against phonon-induced pairing. However, closer examination of the volume dependence of (Formula presented) reveals that the weak variation of (Formula presented)/dP is consistent with moderate (but not weak) electron-phonon coupling.