Two-band Fluctuation Exchange Study on the Superconductivity of β'-(BEDT-TTF)₂ICl₂ under High Pressure

الأصل · EN

We study the pressure dependence of the superconducting transition temperature of an organic superconductor β'-(BEDT-TTF)₂ICl₂ by applying the fluctuation exchange method to the Hubbard model on the original two-band lattice at 3/4-filling rather than the single band model in the strong dimerization limit. Our study is motivated by the fact that hopping parameters evaluated from a first-principles study suggest that the dimerization of the BEDT-TTF molecules is not so strong especially at high pressure. Solving the linearized Eliashberg's equation, a dxy-wave-like superconducting state with realistic values of Tc is obtained in a pressure regime somewhat higher than the actual experimental result. These results are similar to those obtained within the single band model in the previous study by Kino et al. We conclude that the resemblance to the dimer limit is due to a combination of a good Fermi surface nesting, a large density of states near the Fermi level, and a moderate dimerization, which cooperatively enhance electron correlation effects and also the superconducting Tc.