Fingerprints of possible even-parity superconducting states in Sr$_2$RuO$_4$ detected by planar tunneling spectroscopy

TL;DR

This paper proposes a tunneling spectroscopy method to distinguish between three candidate even-parity superconducting states in Sr$_2$RuO$_4$ by analyzing angle-dependent conductance spectra, aiding in identifying the pairing symmetry.

Contribution

It introduces a novel experimental approach using angle-dependent tunneling spectroscopy to differentiate among three leading superconducting states in Sr$_2$RuO$_4$, which was previously unresolved.

Findings

Distinct conductance patterns for each superconducting state.

A practical method to identify pairing symmetry.

Potential to resolve long-standing debate.

Abstract

After more than 25 years of research, three even-parity superconducting states -- the $d+id$-wave, $d+ig$-wave, and $s+id$-wave states -- have emerged as leading candidates for the superconducting states of Sr$_2$RuO$_4$. In the present work, we propose a tunneling spectroscopy experiment for distinguishing among these three superconducting states. The key component of our proposal is that we examine the conductance spectra of normal-metal/Sr$_2$RuO$_4$ junctions with various angles between the junction interface and the crystal axis of the Sr$_2$RuO$_4$. The angle dependence of the conductance spectra shows a unique pattern in each superconducting state, which can function as a fingerprint for verifying the pairing symmetry of Sr$_2$RuO$_4$.