Phase Diagram of the Extended Hubbard Model with Pair Hopping Interaction

A one-dimensional model of interacting electrons with on-site $U$, nearest-neighbor $V$, and pair-hopping interaction $W$ is studied at half-filling using the continuum limit field theory approach. The ground state phase diagram is obtained for a wide range of coupling constants. In addition to the insulating spin- and charge-density wave phases for large $U$ and $V$, respectively, we identify bond-located ordered phases corresponding to an enhanced Peierls instability in the system for $W<0$, $\mathrm{\mid }U-2V\mathrm{\mid }<\mathrm{\mid }2W\mathrm{\mid }$, and to a staggered magnetization located on bonds between sites for $W>0$, $\mathrm{\mid }U-2V\mathrm{\mid }<W$. The general ground state phase diagram including insulating, metallic, and superconducting phases is discussed. A transition to the ${\eta }_{\pi }$-superconducting phase at $\mathrm{\mid }U-2V\mathrm{\mid }\ll 2t\le W$ is briefly discussed.