THEORY OF METAL-INSULATOR-TRANSITION OF DCNQI-CU

We investigate the metal insulator transition of quasi-one dimensional organic conductors (DCNQI)2 Cu by slave boson method. Within mean field approximation, we find that three interactions are needed for these organic conductors getting into insulator phase. These are an on-site Coulomb repulsion on Cu ions, an interaction between conduction electrons and phonons, and Jahn-Teller effect of d-electrons of Cu ions. Also we find that temperature dependence of the free energies of metal state and insulator state agrees with the assumption of our phenomenological theory.