Browsing by Author "Weng, Z. Y."

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    Mobile spin bags and their interaction in the spin-density-wave background
    Weng, Z. Y.; Ting, C. S.; Lee, T. K. (American Physical Society, 1990-02)
    The motion of one doped hole in the spin-density-wave background has been studied by the variational approach. A spin-bag solution for the doped hole has been obtained that applies in the weak- and intermediate-coupling regime. The effective attraction between two spin bags with antiparallel spins has been shown to be p- and d-wave like. The low-lying spin-flip excitations are found to be important both in the spin-bag effect of the doped holes and the effective attraction between them, which, in the latter case, are combined with the exchange of the simple-amplitude fluctuations to give a dominant contribution. On the other hand, the total attractive interaction is reduced by the Coulomb repulsion, which is restored in the presence of the "bag" effect.
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    Path-integral approach to the Hubbard model
    Weng, Z. Y.; Ting, C. S.; Lee, T. K. (American Physical Society, 1991-02)
    A path-integral approach to the Hubbard model is developed for the whole range of the coupling strength U. At half filling, the strong-coupling results are readily reproduced within the simple Gaussian fluctuations. The low-lying spin wave is shown to be described by the nonlinear sigma-model. The effective coupling of the doped hole with the background fluctuations also agrees with that obtained from the t-J model in the small-doping limit. At finite doping, such a formalism may provide a starting point for investigating the short-range spin-liquid state.