Title: Theoretical studies of superconductivity in doped BaCoSO,
Abstract: We investigate superconductivity that may exist in the doped BaCoSO, a
multi-orbital Mott insulator with a strong antiferromagnetic ground state. The
superconductivity is studied in both t-J type and Hubbard type multi-orbital
models by mean field approach and random phase approximation (RPA) analysis.
Even if there is no C4 rotational symmetry, it is found that the system still
carries a d-wave like pairing symmetry state with gapless nodes and sign
changed superconducting order parameters on Fermi surfaces. The results are
largely doping insensitive. In this superconducting state, the three t2g
orbitals have very different superconducting form factors in momentum space. In
particular, the intra-orbital pairing of the dx2-y2 orbital has a s-wave like
pairing form factor. The two methods also predict very different pairing
strength on different parts of Fermi surfaces.These results suggest that BaCoSO
and related materials can be a new ground to test and establish fundamental
principles for unconventional high temperature superconductivity.