Spin Fluctuation-Induced Superconductivity in κ-BEDT-TTF Compounds
arXiv:cond-mat/9903374 · doi:10.1016/S0921-4526(99)00872-8
Abstract
Spin fluctuation-induced superconductivity in quasi-two dimensional organic compounds, κ-BEDT-TTF salts, is investigated within a fluctuation exchange (FLEX) approximation using a half-filled Hubbard model with a right-angled isosceles triangular lattice (transfer matrices -τ, -τ^\prime), extending a previous work above T_c. An energy gap of A_2 or (x^2-y^2)-type develops with decreasing temperature below T_c more rapidly than in the BCS model. The calculated dynamical susceptibilities enough below T_c show sharp resonance peaks like those in certain cuprates superconductors. The calculated nuclear spin-lattice relaxation rate 1/T_1 shows a T^3 behavior below T_c in accordance with experiment. Estimated values of 1/T_1 are roughly consistent with experimental results. A prediction is made for the doping concentration dependence of T_c and the antiferromagnetic and superconductive instability points are calculated in the U/τvs. τ^\prime/τplane.
5 pages, 9 eps figures, uses jpsj.sty