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

C. D. BATISTA AND A. A. ALIGIA

PHYSICAL REVIEW LETTERS

AMER PHYSICAL SOC

Año: 2004 vol. 92 p. 1 - 4

0031-9007

We derive an effective Hamiltonian Heff for an ionic Hubbard chain, valid for tU,, where t is the hopping, U is the Coulomb repulsion, and is the charge-transfer energy. Heff is the minimal model for describing the transition between the band insulator (BI) (?Ut) and the Mott insulator (MI) (U?t). Using spin-particle transformations [Phys. Rev. Lett. 86, 1082 (2001)], we map Heff(U = ) 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 the MI.