Strong electron correlations and ligand hybridization for altermagnetism

TL;DR

This study investigates the electronic origins of altermagnetism in three materials using advanced quantum many-body methods, highlighting the roles of electron correlations and ligand hybridization in enabling this magnetic phenomenon.

Contribution

It demonstrates how local electron correlations and ligand hybridization are essential for realizing altermagnetism in strongly correlated materials.

Findings

MnF$_2$ shows pronounced local correlations and a Mott gap that suppresses spin-band splitting.

MnTe exhibits strong local moments and spin-band splitting due to orbital hybridization.

RuO$_2$ displays itinerant altermagnetic behavior with significant spin-band splitting despite vanishing local moments.

Abstract

Spin-band splitting is a hallmark of altermagnetism, intrinsically linked to magnetic ordering driven by electron correlations. However, recent inconsistencies in the detection of altermagnetism in strongly correlated altermagnet candidates have cast doubt on the robustness of this phenomenon and its dependence on many-body effects. Here, using state-of-the-art quantum many-body frameworks, we dissect the electronic origins of altermagnetism in three prototypical candidates: MnF$_2$, MnTe, and RuO$_2$. In MnF$_2$, we identify pronounced local electron correlations within Mn-3$d$ states and uncover a distinct Mott gap in the visible range, rooted in nonlocal screening effects. The strong correlations markedly localize the Mn-3$d$ electrons, leading to a narrowing of the spin-resolved bandwidth and, consequently, a suppression of spin-band splitting. By contrast, MnTe provides an ideal platform for altermagnetism, exhibiting substantial local Mn-3$d$ magnetic moments due to the strong correlations and pronounced spin-band splitting, enabled by robust Mn 3$d$--Te-5$p$ orbital hybridization. RuO$_2$ manifests as a Pauli paramagnet with vanishing local moments, even in its antiferromagnetic phase. Nonetheless, it exhibits significant spin-band splitting, indicative of itinerant altermagnetic behavior. Our results reveal that both strong local electron correlations and judicious ligand selection to promote orbital hybridization are key prerequisites to realizing altermagnetism in strongly correlated systems. These insights pave the way for the rational design and discovery of novel altermagnetic materials.