Correlation-driven tunability of altermagnetism in RuO$_2$

TL;DR

This study uses advanced theoretical methods to show that electron correlations make RuO$_2$ highly tunable between magnetic phases, explaining experimental discrepancies and enabling control via strain for spintronics applications.

Contribution

The paper demonstrates that dynamical correlation effects are crucial for understanding and tuning the magnetic ground state of RuO$_2$, a prototypical altermagnet.

Findings

DFT+DMFT accurately reproduces experimental spectral functions and optical conductivities.

RuO$_2$ is near a phase boundary, making its magnetic state highly sensitive to external perturbations.

A small compressive strain (~0.5%) can induce an altermagnetic phase.

Abstract

RuO$_2$ has been regarded as a prototypical candidate for metallic altermagnet, offering a potential platform for high-speed and high-efficiency spintronics. However, the magnetic ground state of RuO$_2$ remains a topic of active debate due to conflicting experimental reports. In this work, we investigate the effect of electron correlations in RuO$_2$ using density functional theory combined with dynamical mean-field theory (DFT+DMFT). In contrast to previous DFT-based studies, DFT+DMFT captures essential dynamical correlation effects, yielding spectral functions and optical conductivities in excellent quantitative agreement with experiments, and further reveals that RuO$_2$ resides in the close vicinity of both the paramagnetic-altermagnetic phase boundary and the itinerant-localized crossover, rendering the magnetic ground state highly susceptible to external perturbations. Indeed, even a minimal compressive strain of $\sim$0.5% is sufficient to drive the system into an altermagnetic phase. These findings elucidate the origin of the conflicting experimental observations and reveal that dynamical correlation effects are the key driving force behind the highly tunable magnetic ground state of RuO$_2$.