Path-integral approach to the one-dimensional large-UHubbard model

A path-integral formalism for the one-dimensional Hubbard model in the strong-coupling regime,\udwhich is equivalent to the t-J model in t/U expansion but without any explicit constraint, is developed.\udBased on this formalism, the zero-temperature properties of the Hubbard chain are systematically studied.\udIn the infinite-U limit, the charge and spin degrees of freedom are shown to be completely separated.\udSuch a separation at U= ~ provides a controllable perturbative scheme to study the strongcoupling\udcase. In the large-U regime, the spin degree of freedom is represented by a "squeezed" Heisenberg\udchain. We solve the {squeezed) Heisenberg chain by introducing a soliton representation. Both the\udcharge and spin excitations are found to agree well with the exact solution. The bare electron (hole) is\udshown to be a composite particle of these basic excitations, i.e., holon and spinon, together with a nonlocal\udstring field. This string field makes the electron behave like a "semion" and plays an important role\udin determining various correlation functions. We analytically derive the asymptotic forms of the spinspin\udand density-density correlation functions as well as the single-electron and the pair-electron Green's\udfunctions. The implications of the present work to the two-dimensional model are discussed