Theory of chiral $p$-wave superconductivity with near-nodes for Sr$_2$RuO$_4$

TL;DR

This paper uses the functional renormalization group to study a three-orbital model of Sr$_2$RuO$_4$, revealing chiral p-wave pairing with near-nodes caused by spin-orbit coupling, explaining experimental discrepancies.

Contribution

It provides a theoretical explanation for the coexistence of d-wave-like thermal features and chiral p-wave pairing in Sr$_2$RuO$_4$ due to near-nodes induced by spin-orbit coupling.

Findings

Chiral p-wave pairing is dominant in the model.

Atomic spin-orbit coupling induces near-nodes.

The theory reconciles different experimental observations.

Abstract

We use functional renormalization group method to study a three-orbital model for superconducting Sr$_2$RuO$_4$. Although the pairing symmetry is found to be chiral $p$-wave, the atomic spin-orbit coupling induces near-nodes for quasiparticle excitations. Our theory explains a major experimental puzzle between $d$-wave-like feature observed in thermal experiments and the chiral $p$-wave triplet pairing revealed in nuclear-magnetic-resonance and Kerr effect.