Transverse and in-plane modification of superconductivity and electronic structure in the quasi-two-dimensional organie conductor K-(BEDT-TTF)2CU(SCN)2 by uniaxial stress

Abstract We have employed uniaxial stress along the principal axes of the quasi-two-dimensional organie superconductor κ-(BEDT-TTF)2CU(SCN)2 (BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene). The lattice anisotropy is thereby altered, with corresponding changes in the intermolecular transfer energies. The effect of uniaxial stress on the superconducting transition temperature Tc and critical field Bc2 is found to be anisotropic. There is an indication of an inerease in Tc and an inerease in Bc2 for in-plane stress, but both parameters decrease rapidly for transverse (interplane) stress. Magnetotransport studies reveal stress-induced changes in the Fermi surface through the observation of the Shubnikov-de Haas oscillations. The stress dependence of a resistive anomaly in the magnetoresistance, which is associated with the critical field Bc2 , is also investigated. We discuss the experimental findings in the context of recent phenomenological and theoretical treatments of quasi-two-dimensional systems where the anisotropic triangular-lattice Hubbard model has been used to treat two-dimensional superconductors.