Strong-coupling expansions for the anharmonic Holstein model and for the Holstein-Hubbard model

Article

关键词: INFINITE DIMENSIONS;    SUPERCONDUCTIVITY;    ATTRACTION;    SYMMETRY;    SYSTEMS;    STATE;   

DOI  :  10.1103/PhysRevB.54.9372

来源: SCIE

【 摘 要 】

A strong-coupling expansion is applied to the anharmonic Holstein model and to the Holstein-Hubbard model through fourth order in the hopping matrix element. Mean-field theory is then employed to determine transition temperatures of the effective (pseudospin) Hamiltonian. We find that anharmonic effects are not easily mimicked by an on-site Coulomb repulsion and that anharmonicity strongly favors superconductivity relative to charge-density-wave order. Surprisingly, the phase diagram is strongly modified by relatively small values of the anharmonicity.

【 授权许可】

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