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Phase diagram of the extended Hubbard chain with charge-dipole interactions

M. E. Torio·A. A. Aligia·K. Hallberg·H. A. Ceccatto
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Abstract

We consider a modified extended Hubbard model (EHM) which, in addition to the on-site repulsion U and nearest-neighbor repulsion V, includes polarization effects in second-order perturbation theory. The model is equivalent to an EHM with renormalized U plus a next-nearest-neighbor repulsion term. Using a method based on topological quantum numbers (charge and spin Berry phases), we generalize to finite hopping t the quantum phase diagram in one dimension constructed by van den Brink et al. (Phys. Rev. Lett. 75, 4658 (1995)). At hopping t=0 there are two charge density-wave phases, one spin density-wave phase and one intermediate phase with charge and spin ordering, depending on the parameter values. At t \neq 0 the nature of each phase is confirmed by studying correlation functions. However, in addition to the strong-coupling phases, a small region with bond ordering appears. The region occupied by the intermediate phase first increases and then decreases with increasing t, until it finally disappears for t of the order but larger than U. For small t, the topological transitions agree with the results of second order perturbation theory.

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M. E. Torio, A. A. Aligia, K. Hallberg, H. A. Ceccatto. 2000-09-04. Phase diagram of the extended Hubbard chain with charge-dipole interactions. https://doi.org/10.1103/physrevb.62.6991

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