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arXiv · 1803.05224

Excitonic Order and Superconductivity in the Two-Orbital Hubbard Model: Variational Cluster Approach

Ryo Fujiuchi·Koudai Sugimoto·Yukinori Ohta
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Abstract

Using the variational cluster approach based on the self-energy functional theory, we study the possible occurrence of excitonic order and superconductivity in the two-orbital Hubbard model with intra- and inter-orbital Coulomb interactions. It is known that an antiferromagnetic Mott insulator state appears in the regime of strong intra-orbital interaction, a band insulator state appears in the regime of strong inter-orbital interaction, and an excitonic insulator state appears between them. In addition to these states, we find that the $s^{\pm}$-wave superconducting state appears in the small-correlation regime, and the $d_{x^2 - y^2}$-wave superconducting state appears on the boundary of the antiferromagnetic Mott insulator state. We calculate the single-particle spectral function of the model and compare the band gap formation due to the superconducting and excitonic orders.

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Ryo Fujiuchi, Koudai Sugimoto, Yukinori Ohta. 2018-03-14. Excitonic Order and Superconductivity in the Two-Orbital Hubbard Model: Variational Cluster Approach. https://doi.org/10.7566/jpsj.87.063705

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