ASYMMETRIC HUBBARD CHAIN AT HALF-FILLING

The ground-state phase diagram of the one-dimensional asymmetric Hubba rd model at half-filling is studied by means of a perturbation expansi on in the large-U limit and White's density matrix renormalization-gro up method for various values of the couplings. We argue that the intro duction of asymmetry in the hopping parameters is a relevant perturbat ion for any repulsive U and drives the system into an ordered Neel ant iferromagnet. The transition belongs to the Kosterlitz-Thouless univer sality class.