Excitonic insulator state in the two-orbital Hubbard model: Variational cluster approach

T. Kaneko, K. Seki, and Y. Ohta
Phys. Rev. B 85, 165135 – Published 23 April 2012

Abstract

The variational cluster approximation is used to study the spontaneous symmetry breaking of the excitonic insulator (EI) state in the two-orbital Hubbard model defined on the two-dimensional square lattice. Evaluating the order parameter of the EI state, staggered magnetization, and number of particles on each orbital, we obtain the ground-state phase diagram of the model in a wide parameter space of the intra and interorbital Coulomb interactions. We also calculate the single-particle and anomalous Green's functions. We show that the normal metallic phase is unstable to the formation of the EI state and the EI phase appears in a wide parameter region between the band-insulator and Mott-insulator phases.

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  • Received 14 March 2012

DOI:https://doi.org/10.1103/PhysRevB.85.165135

©2012 American Physical Society

Authors & Affiliations

T. Kaneko, K. Seki, and Y. Ohta

  • Department of Physics, Chiba University, Chiba 263-8522, Japan

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Issue

Vol. 85, Iss. 16 — 15 April 2012

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