Realization of a mixed-symmetry superconducting gap in correlated organic metals
ORAL
Abstract
Recent scanning tunneling spectroscopy measurements on the organic charge tranfer salt $\kappa$-(BEDT-TTF)$_2$Cu[N(CN)$_2$]Br show clear evidence of a highly anisotropic gap structure. Based on an {\it ab initio} derived model Hamiltonian we employ random phase approximation spin fluctuation theory yielding a composite order parameter of (extended) s+d$_{x^2-y^2}$ symmetry. Taking explicitly also the shape of the Fermi surface into account we calculate STS spectra that are in excellent agreement to the experimental observations [1]. Moreover we determine the minimal tight binding model to describe the general lattice structure of these compounds accurately and generate a phase diagram for the gap symmetry by varying the hopping parameters. Based on {\it ab initio} derived parameter sets we predict the gap symmetry of other superconducting $\kappa$ charge transfer salts.
*This work was supported by Deutsche Forschungsgemeinschaft under Grant No. SFB/TR 49.
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