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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