Selection Rule in Josephson Coupling between In and Sr2RuO4

TL;DR

This study investigates the directional Josephson coupling between In and Sr2RuO4, revealing a symmetry-based selection rule that constrains the superconducting order parameter's nature in Sr2RuO4.

Contribution

It provides experimental evidence for the symmetry of Sr2RuO4's order parameter, supporting a p-wave pairing state with specific spin and orbital characteristics.

Findings

Coupling allowed in-plane but not along c axis

Supports p-wave pairing symmetry in Sr2RuO4

Suggests a nodeless, in-plane spin orientation state

Abstract

We have studied the Josephson coupling between a conventional s-wave superconductor (In) and Sr2RuO4 and found that the coupling is allowed in the in-plane direction, but not along the c axis. This selection rule indicates that the symmetry of superconducting order parameter of Sr2RuO4 is either p- or alternatively, purely d-wave. If Sr2RuO4 is a p-wave superconductor, as strongly favored by other experimental evidence, our result suggests that the pairing state of Sr2RuO4 is Gamma5 with d(k) = z(kx +/- iky), a nodeless state in which the spins of the superconducting electrons lie in the RuO2 planes.