Distinct pairing symmetries of superconductivity in infinite-layer nickelates

Abstract

We report theoretical predictions on the pairing symmetry of the newly discovered superconducting nickelate ${\mathrm{Nd}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{NiO}}_{2}$ based on the renormalized mean-field theory for a generalized model Hamiltonian. For practical values of the key parameters, we find a transition between a gapped ($d+is$)-wave pairing state in the small doping region to a nodal $d$-wave pairing state in the large doping region, accompanying with an abrupt Fermi surface change at the critical doping. Our overall phase diagram also shows the possibility of a ($d+is$)- to $s$-wave transition if the electron hybridization is relatively small. In either case, the low-doping ($d+is$)-wave state is a gapped superconducting state with broken time-reversal symmetry. Our results are in qualitative agreement with recent experimental observations and predict several key features to be examined in future measurements.