Fermi-liquid behavior and characteristic temperature-dependent susceptibility in clean RuO$_2$ crystal

TL;DR

This study investigates the magnetic and electronic properties of ultra-clean RuO₂ crystals, revealing Fermi-liquid behavior and a characteristic temperature-dependent susceptibility linked to lattice effects.

Contribution

It provides new experimental evidence of Fermi-liquid behavior and temperature-dependent susceptibility in high-quality RuO₂ crystals, highlighting the role of lattice-induced band structure changes.

Findings

Magnetic susceptibility increases with temperature up to 400 K.

Susceptibility fitted with a T ln(T/T₀) dependence over wide temperature range.

Electronic specific heat and resistivity indicate weakly-correlated 3D Fermi-liquid state.

Abstract

The magnetic nature of the altermagnet candidate RuO$_2$ remains under debate. It has been recently shown from quantum oscillations and angle-resolved photoemission spectroscopy (ARPES) that the high-quality RuO$_2$ bulk single crystal is a paramagnetic metal. Here we report the specific heat and magnetic susceptibility in ultra-clean RuO$_2$ single crystals with residual resistivity ratio up to 1200. The magnetic susceptibility increases with temperature and is phenomenologically fitted with an inclusion of $T\textrm{ln}(T/T_0)$ over a wide temperature range up to 400 K. In contrast, the energy dependence of the density of states and thermal activation of quasiparticles lead to a decrease with temperature. Such characteristic temperature dependence, similar to that observed in other $d$-electron metals, is attributable to an enhanced orbital contribution arising from lattice-expansion-induced changes in the band structure. The electronic specific heat, the magnetic susceptibility, and the $T^2$ coefficient in resistivity point to a weakly-correlated 3D Fermi-liquid state with a modest electron correlation, as supported by the Wilson and Kadowaki-Woods ratios.