Relationship between effective mass and superconducting critical temperature in the organic superconductor κ-(BEDT-TTF)2Cu(NCS)2

We report high pressure magnetotransport on the organic superconductor κ-(BEDT-TTF)2Cu(NCS)2. The observation of Shubnikovde Haas and magnetic breakdown oscillations has allowed the pressure dependences of the Fermi surface topology and quasiparticle effective masses to be deduced and compared with simultaneous measurements of the superconducting critical temperature Tc. The data strongly suggest that the enhancement of the effective mass and the superconducting behaviour are directly connected. The results are fitted by calculations of the linearised Eliashberg equations.