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, $U_c(\kappa=0)=W >0$.
Categories: cond-mat