Pairing symmetry in a two-orbital Hubbard model on a square lattice

Katsunori Kubo
Phys. Rev. B 75, 224509 – Published 14 June 2007

Abstract

We investigate superconductivity in a two-orbital Hubbard model on a square lattice by applying fluctuation exchange approximation. In the present model, the symmetry of the two orbitals are assumed to be that of an s orbital. Then, we find that an s-wave spin-triplet orbital-antisymmetric state and a p-wave spin-singlet orbital-antisymmetric state appear when Hund’s rule coupling is large. These states are prohibited in a single-orbital model within states with even frequency dependence, but allowed for multiorbital systems. We also discuss pairing symmetry in other models which are equivalent to the two-orbital Hubbard model except for symmetry of orbitals. Finally, we show that pairing states with a finite total momentum, even without a magnetic field, are possible in a system with two Fermi surfaces.

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  • Received 26 December 2006

DOI:https://doi.org/10.1103/PhysRevB.75.224509

©2007 American Physical Society

Authors & Affiliations

Katsunori Kubo

  • Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan

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Issue

Vol. 75, Iss. 22 — 1 June 2007

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