dx2-y2- versus dxy- like pairings in organic superconductors κ-(BEDT-TTF)2X -: art. no. 100516

Pairing symmetry in kappa-(BEDT-TTF)(2)X is reexamined by applying the fluctuation exchange method to the Hubbard model on the original four-band lattice. Our study is motivated by the discrepancy between recent thermal conductivity/tunneling spectroscopy experiments and the previous theories based on the effective single or two-band model. In contrast to the previous theories, we find that d(x)2-(y)2-like pairing dominates over d(xy) in agreement with recent experiments. Our study provides a general lesson that even if the Fermi surface seems to be reproduced by an effective model, the pairing symmetry can be different from that of the original system.