Distinct pairing symmetries of superconductivity in infinite-layer nickelates

TL;DR

This paper predicts the pairing symmetries in superconducting nickelates, revealing a transition from a gapped ($d+is$)-wave to a gapless $d$-wave state with doping, aligning with recent experiments.

Contribution

It provides a theoretical phase diagram of pairing symmetries in nickelates, highlighting transitions influenced by doping and hybridization, which was not previously detailed.

Findings

Transition from ($d+is$)-wave to $d$-wave pairing with doping

Abrupt Fermi surface change at critical doping

Possible ($d+is$)- to $s$-wave transition with small hybridization

Abstract

We report theoretical predictions on the pairing symmetry of the newly discovered superconducting nickelate Nd$_{1-x}$Sr$_{x}$NiO$_{2}$ based on the renormalized mean-field theory for a generalized model Hamiltonian proposed in [Phys. Rev. B \textbf{101}, 020501(R)]. 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 gapless $d$-wave pairing state in the large doping region, accompanied by 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.