Role of Bond-Bond Interaction in the Extended Hubbard Chain

Abstract

Phase diagram of the one-dimensional extended Hubbard model with a nearest neighbor interaction V and site-off-diagonal (bond-charge X and bond-bond W) interactions at half-filling is obtained analytically and numerically. For the numerical analysis, we used the level-crossing approach which has been applied to the W=0 case [Phys. Rev. B 61 (2000) 16377]. Similarly to the X term, the W term enhances bond-charge-density-wave (BCDW) and bond-spin-density-wave (BSDW) phases for W<0 and W>0 cases, respectively. In addition, we showed that an exact ground state corresponding to a BSDW state, and an η-pairing ground state appear in this model.