Theoretical investigation of the superconducting pairing symmetry in a bilayer two-orbital model of pressurized La₃Ni₂O₇

We investigate the superconducting pairing symmetry in pressurized La₃Ni₂O₇based on a bilayer two-orbital model. There are two symmetric bands<i>α</i>and<i>γ</i>, as well as two antisymmetric ones<i>β</i>and<i>δ</i>. It is found that the<i>γ</i>band induces considerable ferromagnetic spin fluctuation and prefers an odd-frequency,<i>s</i>-wave spin triplet pairing state. The addition of the other bands gradually enhances some antiferromagnetic spin fluctuations which eventually surpass the ferromagnetic one. The superconducting pairing then evolves from a spin triplet into a<i>d</i>-wave spin singlet, and finally into ans±-wave one. The competition between the<i>d</i>-wave ands±-wave pairings relies on the relative strength of the ferromagnetic spin fluctuation to the antiferromagnetic ones.