Possible pairing states in the superconducting bilayer nickelate

Abstract

We examine various possibilities for the pairing mechanisms in the recently discovered bilayer-nickelate superconductor within the Bardeen-Cooper-Schrieffer framework. Unlike earlier studies, where only a pure $d$-wave or sign-changing $s$-wave superconductivity instability was investigated, our study explores the possibilities of mixed-state superconducting instability such as the one involving both $d$- and sign-changing $s$-waves. While assuming that the superconductivity arises because of the magnetic correlations, we examine the nature of the superconducting gap function associated density of states with various possible magnetic correlation wavevectors arising out as a result of multiple pockets owing to the multiple orbitals and bilayer splitting. We also explore the effect of differences in the nature of Fermi surfaces suggested by various studies.