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Superconductivity in eg orbital systems with multi-Fermisurface

KATSUNORI KUBO1,*

Affiliation

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

Abstract

We study superconductivity in eg orbital systems on a square lattice by applying fluctuation exchange approximation. For such a multiorbital system, even-parity spin-triplet and odd-parity spin-singlet states are allowed by constructing a pair with antisymmetrical orbitals. Indeed, it has been found that such states appear in a two-orbital Hubbard model in which Fermi surfaces for both orbitals are the same. In the eg orbital model, the number of Fermi surfaces and their structures depend on the ratio of the Slater-Koster integrals, and exotic superconducting states peculiar to a multi-Fermi-surface system may occur. We find several superconducting states depending on the structure of the Fermi surfaces and the number of electrons per site. In particular, we find even-parity spin-triplet and odd-parity spin-singlet states with a finite total momentum like the Fulde-Ferrell-Larkin-Ovchinnikov state even without a magnetic field. Such an exotic pair can be stabilized with a finite total momentum, which connects the centers of Fermi surfaces with similar structures..

Keywords

Fulde-Ferrell-Larkin-Ovchinnikov state, Orbital degree of freedom, Fluctuation exchange approximation.

Submitted at: April 1, 2008
Accepted at: July 1, 2008

Citation

KATSUNORI KUBO, Superconductivity in eg orbital systems with multi-Fermisurface, Journal of Optoelectronics and Advanced Materials Vol. 10, Iss. 7, pp. 1683-1687 (2008)