Superconductivity in e orbital systems with multi-Fermi-surface

Kubo, Katsunori

Journal of Optoelectronics and Advanced Materials, 10(7), p.1683 - 1687, 2008/07

We study superconductivity in e 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, such states appear in a two-orbital Hubbard model with the same Fermi surface for both orbitals. In the present e orbital model, there is another important feature: the number of Fermi surfaces and their structures depend on the ratio of the Slater-Koster integrals. Then, we find even-parity spin-triplet and odd-parity spin-singlet states with a finite total momentum like the Fulde-Ferrell-Larkin-Ovchinnikovstate even without a magnetic field. When two Fermi surfaces have structures similar to each other, such an exotic pair with a finite total momentum, which connects the centers of the Fermi surfaces, can be stabilized.