J. Phys. IV France
Volume 114, April 2004
Page(s) 245 - 249

J. Phys. IV France
114 (2004) 245
DOI: 10.1051/jp4:2004114052

The superconducting order parameter in the organic layered superconductor $\kappa
$ -(BEDT-TTF) 2Cu[ N(CN) 2] Br

M. Pinteric1, 2, S. Tomic1 and K. Maki3

1  Institut za fiziku, Zagreb, Croatia
2  Faculty of Civil Engineering, University of Maribor, Slovenia
3  Department of Physics and Astronomy, USC, Los Angeles, USA

Highly sensitive ac susceptibility measurements were performed in order to resolve the controversy regarding the symmetry of the superconducting order parameter in $\kappa
$-BEDT-TTF materials. The experimentally obtained superfluid density behaviour qualitatively contradicts s-wave symmetry theoretical predictions, but disagrees also quantitatively with the d-wave expected behaviour in the weak coupling limit. The mixture of d-wave and s-wave parameters, with a rather large proportion of the latter, describes well the results; however, it also opens new questions regarding the origin of the superconducting pairing. Key words. organic superconductivity, ac susceptibility, magnetic penetration depth.

© EDP Sciences 2004