International Journal of Modern Physics B

THE EFFECT OF A BOND-SITE INTERACTION ON THE GROUND-STATE INSTABILITIES OF THE ONE-DIMENSIONAL HUBBARD MODEL

Florin D. Buzatu

Published May 30, 1995• 3 citations

Abstract

The ground-state instabilities for a one-dimensional lattice system of electrons with onsite (Hubbard) and bond-site (hopping) interactions are analyzed in a perturbative approach. The zero temperature phase diagram at different band fillings is drawn; an attractive (repulsive) bond-site interaction favors the appearance of a superconductor state at low concentrations of electrons (holes). A comparison with the exact results for the Hubbard model and previous works for particular cases is also discussed.

DOI: 10.1142/s0217979295000653

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International Journal of Modern Physics B

THE EFFECT OF A BOND-SITE INTERACTION ON THE GROUND-STATE INSTABILITIES OF THE ONE-DIMENSIONAL HUBBARD MODEL

Florin D. Buzatu

Published May 30, 1995• 3 citations

Publisher

Abstract

DOI: 10.1142/s0217979295000653

Related papers

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{\mathit{U}}_{\mathit{c}}

(n), although no explicit attraction between particles is present in the Hamiltonian. The presence of a bound state for two particles in vacuum in D=1 and 2 (but not for D=3) suggests that, at low density and low dimensionality, superconductivity is due to condensation of preexistent pairs (dimers). The one-dimensional (1D) phase diagram is studied analytically as well as numerically and shows a transiiton between a Luttinger liquid and a strong-coupling phase with diverging superconducting susceptibility. Estimates of critical exponents are given at low density and at quarter filling for several values of the parameters. The 2D model at quarter filling is analyzed by Lanczos diagonalization on a 4\ifmmode\times\else\texttimes\fi{}4 cluster. The numerical results are consistent with the phase diagram obtained by BCS mean-field theory and is qualitatively similar to the 1D case: a ground state with spin gap and off-diagonal long-range order at U

{\mathit{U}}_{\mathit{c}}

(n); and a Fermi liquid above

{\mathit{U}}_{\mathit{c}}

with no sign of phase separation.

A one-dimensional model of interacting electrons with on-site U, nearest-neighbor V, and correlated-hopping interaction

{T}^{*}

is studied at half filling using the continuum-limit field theory approach. The ground-state phase diagram is obtained for a wide range of coupling constants. In addition to the insulating spin- and charge-density wave phases for large U and V, respectively, we identify bond-located ordered phases corresponding to an enhanced Peierls instability in the system for ${T}^{*}>0, |U\ensuremath{-}2V|<{8T}^{*}/\ensuremath{\pi}$ and to a staggered magnetization located on bonds between sites for ${T}^{*}<0, |U\ensuremath{-}2V|<8|{T}^{*}|/\ensuremath{\pi}.$ The general ground-state phase diagram including insulating, metallic, and superconducting phases is discussed.