Probing Pairing Symmetry in Sr$_2$RuO$_4$

TL;DR

This paper investigates the spin dynamics in Sr$_2$RuO$_4$ to identify its pairing symmetry, proposing a unique collective mode as a signature of p-wave superconductivity that breaks time reversal symmetry.

Contribution

It introduces a novel collective mode in the spin channel specific to p-wave pairing, offering a new method to determine the pairing symmetry in Sr$_2$RuO$_4$.

Findings

Identified a collective spin mode at the nesting vector in the p-wave phase.

Mode is absent in s- and d-wave superconductors.

Proposed using this mode as a probe for pairing symmetry.

Abstract

We study the spin dynamics in a p-wave superconductor at the nesting vector associated with $\alpha$ and $\beta$ bands in Sr$_2$RuO$_4$. We find a collective mode at the nesting vector in the superconducting phase identified as the odd-parity pairing state which breaks time reversal symmetry. This mode in the spin channel only exists in the p-wave superconductor, not in s- or d-wave superconductors. We propose that probing this mode would clarify the pairing symmetry in Sr$_2$RuO$_4$. The possibility of second superconducting phase transition is also discussed.