Multipole-fluctuation pairing mechanism of dx2-y2+ig superconductivity in Sr2RuO4

Despite many experimental and theoretical efforts, the pairing symmetry of superconductivity in Sr2RuO4 remains undecided. The accidentally degenerate dx2-y2 + ig is consistent with most current experiments and seems to be one of the most probable candidates, but we still lack a satisfactory theoretical mechanism for its appearance. Here we construct a phenomenological model combining realistic electronic band structures and all symmetry-allowed multipole fluctuations as potential pairing glues and make a systematic survey of major pairing states within the Eliashberg framework. Our calculations show that dx2-y2 + ig can arise naturally from the interplay of antiferromagnetic, ferromagnetic, and electric multipole fluctuations whose coexistence is manifested in previous experiments and calculations. Our work provides a physically reasonable basis supporting the possibility of dx2-y2 + ig pairing in superconducting Sr2RuO4.

Automated summary

Despite ongoing experimental and theoretical efforts, the pairing symmetry of superconductivity in Sr2RuO4 remains uncertain. In this study, a phenomenological model combining realistic electronic band structures and all symmetry-allowed multipole fluctuations was constructed to investigate potential pairing states within the Eliashberg framework. The findings suggest that the dx2-y2 + ig pairing state can naturally arise from the interplay of various types of fluctuations, including antiferromagnetic, ferromagnetic, and electric multipole fluctuations.