ASYMPTOTIC BETHE-ANSATZ RESULTS FOR 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 r). Assuming integrability, the asymptotic-Bethe-ansatz approach allows us to derive the generalized Lieb-Wu integral equations from the two-particle phase shift. Due to the nesting property there is a metal-to-insulator transition at U-c (kappa > 0) = 0(+). The charge gap in the singular limit kappa = 0 opens when the interaction strength equals the bandwidth, U-c (kappa = 0) = W > 0.