Schedule Nov 21, 2002
Pairing and magnetic correlations in quasi-two-dimensional organic superconductors
Joerg Schmalian, Iowa State
In the first part of the talk I will review electronic and magnetic properties of quasi-two-dimensional organic superconductors. Particular emphasis will be given to the role of magnetic correlations as well as to experiments indicating what the nature of the pairing state is. Even though the issue of the pairing symmetry is still controversial, I will argue that there are strong indications for unconventional superconductivity. In the second part I will show that for a \kappa-type organic (BEDT-TTF)_2-X molecular crystal, a superconducting state with T_c ~ 10 K and gap nodes on the Fermi surface can be caused by short-ranged antiferromagnetic spin fluctuations. Using a two-band description for the anti-bonding orbitals on a BEDT-TTF dimer of the \kappa-type salt, and a Coulomb repulsion between two holes on one dimer, the magnetic interaction and the superconducting gap-function are determined. It is shown that the pairing interaction is predominantly caused by inter-band coupling and additionally affected by spin excitations of the quasi one-dimensional band.

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