paper

Exact Bond Ordered Ground State for the Transition Between the Band and the Mott Insulator

arXiv:cond-mat/0309295 · doi:10.1103/PhysRevLett.92.246405

Abstract

We derive an effective Hamiltonian for an ionic Hubbard chain, valid for , where is the hopping, the Coulomb repulsion, and the charge transfer energy. is the minimal model for describing the transition from the band insulator (BI) () and the Mott insulator (MI) (). Using spin-particle transformations (Phys. Rev. Lett. \textbf{86}, 1082 (2001)), we map into an SU(3) antiferromagnetic Heisenberg model whose exact ground state is known. In this way, we show rigorously that a spontaneously dimerized insulating ferroelectric phase appears in the transition region between the BI and MI.

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