Modulating effect of pair-hopping and spin exchange interactions on a half-filled generalized U–V chain

Abstract

In this paper, we study analytically a half-filled generalized Hubbard chain with a quite general nearest-neighbor interaction, parametrized by diagonal repulsion V, off-diagonal pair-hopping and correlated-hopping repulsions W, X and antiferromagnetic spin exchange J for small values of the interactions. The ground state phase diagram is obtained in the weak-coupling regime. Besides the charge-density-wave (CDW) and spin-density-wave (SDW) phases for large 2V/U and U/2V, respectively, we identify a bond-spin-density-wave (BSDW) for J/W < 2, 3J/2 - 2W < 2V - U < 2W - J/2 and bond-charge-density-wave (BCDW) phase for J/W > 2, 2W - J/2 < 2V - U < 3J/2 - 2W. The modulating effect of W and J is responsible for the emergence of BSDW and BCDW phases, which, however, are decreased weakly by the Umklapp scattering of parallel-spin electrons.