Fermi-liquid behavior of non-altermagnetic RuO$_2$

TL;DR

This study demonstrates that RuO$_2$ exhibits Fermi-liquid behavior and is best described as a paramagnetic metal with weak electronic correlations, based on optical spectroscopy and band-structure calculations.

Contribution

The paper provides evidence that RuO$_2$ is a nonmagnetic, paramagnetic metal with Fermi-liquid properties, challenging previous debates about its magnetism and altermagnetic nature.

Findings

Optical conductivity matches nonmagnetic model predictions.

Presence of a Dirac nodal line 45 meV below Fermi level.

Fermi-liquid behavior with two scattering rates below 150 K.

Abstract

Presence of magnetism in potentially altermagnetic RuO$_2$ has been a subject of intense debate. Using broadband infrared spectroscopy combined with density-functional band-structure calculations, we show that optical conductivity of RuO$_2$, the bulk probe of its electronic structure, is well described by the nonmagnetic model of this material. The sharp Pauli edge demonstrates the presence of a Dirac nodal line lying 45 meV below the Fermi level. Good match between the experimental and ab initio plasma frequencies underpins weakness of electronic correlations. The intraband part of the optical conductivity indicates Fermi-liquid behavior with two distinct scattering rates below 150 K. Fermi-liquid theory also accounts for the temperature-dependent magnetic susceptibility of RuO$_2$ and allows a consistent description of this material as paramagnetic metal.