Degenerate three-band Hubbard model with anti-Hund's rule interactions: A model for A(x)C(60)

Article

关键词: NARROW ENERGY BANDS;    ELECTRON CORRELATIONS;    DOPED FULLERENES;    MOTT INSULATORS;    TRANSITION;    SUPERCONDUCTIVITY;    A(4)C(60);    RB4C60;    NMR;    PRESSURE;   

DOI  :  10.1103/PhysRevB.68.205107

来源: SCIE

【 摘 要 】

We consider the orbitally degenerate three-band Hubbard model with on-site interactions which favor low spin and low orbital angular momentum using standard second-order perturbation theory in the large Hubbard-U limit. At even-integer filling this model is a Mott insulator with a nondegenerate ground state that allows for a simple description of particle-hole excitations as well as gapped spin and orbital modes. We find that the Mott gap is generally indirect and that the single-particle spectrum at low doping reappears close to even filling but rescaled by a factor of 2/3 or 1/3. The model captures the basic phenomenology of the Mott insulating and metallic fullerides A(x)C(60). This includes the existence of a smaller spin gap and larger charge gap at even-integer filling, the fact that odd-integer stoichiometries are generally metallic while even integer are insulating, as well as the rapid suppression of the density of states and superconducting transition temperatures with doping away from x=3.

【 授权许可】

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