HOLE DYNAMICS IN A SPIN BACKGROUND - A SUM-RULE-CONSERVING THEORY WITH EXACT LIMITS

Article

关键词: U=INFINITY HUBBARD-MODEL;    QUANTUM ANTIFERROMAGNET;    SPECTRAL-FUNCTION;    STATE;    INSULATORS;    SUPERCONDUCTIVITY;    CONDUCTIVITY;    EXCITATIONS;    DIMENSIONS;    SYSTEMS;   

DOI  :  10.1103/PhysRevB.45.2237

来源: SCIE

【 摘 要 】

A self-consistent theory is formulated for the dynamics of a hole moving in a d-dimensional, quantum-mechanical background of spins at arbitrary temperatures. The contribution of loops in the path of a hole, which are always important in dimensions d > 1, is given particular attention. We first show that the Green function, thermodynamics, and dynamical conductivity can be determined exactly in the limit d --> infinity. On the basis of this solution, we construct an approximation scheme for the dynamics of a hole in dimensions d < infinity, where loops are summed self-consistently to all orders. The resulting theory satisfies the spectral and f-sum rules and yields the exact solution for the ferromagnetic background in any dimension d. Three types of spin backgrounds are explicitly discussed: ferromagnetic, Neel, and random. In the Neel case the retraceable-path approximation by Brinkman and Rice for the Green function is found to be correct up to order 1/d4 for large d. Detailed calculations of the density of states D(omega) and the conductivity sigma(omega) of the hole are presented for d = 3 and infinity. A characteristic dependence on the particular type of spin background is found, which is especially pronounced in the case of sigma(omega).

【 授权许可】

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