Probing active/passive bands by quasiparticle interference in Sr$_{2}$RuO$_{4}$

TL;DR

This paper theoretically investigates quasiparticle interference in Sr$_{2}$RuO$_{4}$ to distinguish between two pairing models, proposing an experimental approach to identify active/passive bands and topological nature.

Contribution

It introduces a method to differentiate pairing models in Sr$_{2}$RuO$_{4}$ using QPI patterns, aiding in resolving band activity and topological superconductor debates.

Findings

QPI peaks evolve with energy in the $\gamma$ band model.

QPI spectra are dispersionless in the $\alpha$ and $eta$ bands model.

QPI behavior can help identify active/passive bands and topological properties.

Abstract

The quasiparticle interference (QPI) in Sr$_{2}$RuO$_{4}$ is theoretically studied based on two different pairing models in order to propose an experimental method to test them. For a recently proposed two-dimensional model with pairing primarily from the $\gamma$ band, we found clear QPI peaks evolving with energy and their locations can be determined from the tips of the constant-energy contour (CEC). On the other hand, for a former quasi-one-dimensional model with pairing on the $\alpha$ and $\beta$ bands, the QPI spectra are almost dispersionless and may involve off-shell contributions to the scatterings beyond the CEC. The different behaviors of the QPI in these two models may help to resolve the controversy of active/passive bands and whether Sr$_{2}$RuO$_{4}$ is a topological superconductor.