Abstract. We present a group theoretical analysis of several classes of organic superconductor. We predict that highly frustrated organic superconductors, such as κ-(ET)₂Cu₂(CN)₃ (where ET is BEDT-TTF, bis(ethylene-dithio)tetrathiafulvalene) and β'-[Pd(dmit)₂]₂X, undergo two superconducting phase transitions, the first from the normal state to a d-wave superconductor and the second to a d+id state. We show that the monoclinic distortion of κ-(ET)₂Cu(NCS)₂ means that the symmetry of its superconducting order parameter is different from that of orthorhombic κ-(ET)₂Cu[N(CN)₂]Br. We propose that β'' and θ phase organic superconductors have d_xy+s order parameters.

Print publication: Issue 46 (22 November 2006)
Received 10 August 2006, in final form 14 September 2006
Published 3 November 2006