ASYMPTOTIC BETHE-ANSATZ RESULTS FOR A HUBBARD CHAIN WITH 1/SINH-HOPPING

We investigate spin-1/2 electrons with local Hubbard interaction and variable range hopping amplitudes which decay like sinh(kappa)/sinh(kappa tau). Using Sutherland's Asymptotic Bethe Ansatz we derive the generalized Lieb-Wu integral equations from the two-particle phase shift. For half-filling we obtain a closed expression for the ground state energy density. Due to the nesting property there is a metal-to-insulator transition at U-c(kappa > 0) = 0(+). In the singular limit kappa = 0 the charge gap opens when the interaction strength equals the bandwidth, U-c(kappa = 0) = W.