Metallic, Insulating and Superconducting States in κ-ET_2X Systems, where ET is the BEDT- TTF (bis(ethylenedithio)tetrathiafulvalene) molecule

摘要

An electronic structure and normal and superconducting properties are reviewed for layered organic materials on the basis of bis(ethylenedithio)tctrathiafulvalene molecule (BEDT-TTF. hereafter ET) with essential intraET electron and cross-dimer κ-packing in ET-plane. The metall-insulator phase transition is derived for realistic model of κ-ET_2X salts. Based on the Fermi-surface topology and electron correlations the d-symmetry of superconducting order parameter is obtained with interplay between its nodes on the Fermi surface and superconducting phase characteristics. The results are in agreement with measured nonactivated temperature dependencies of NMR-relaxation rate of central carbon ~(13)C spins in ET and superconducting specific heat.