Correlation-Driven Orbital Order Realizes 2D Metallic Altermagnetism

TL;DR

This paper demonstrates that electronic correlation-driven orbital order can induce 2D metallic altermagnetism with large spin splitting, exemplified by monolayer YbMn2Ge2, offering a new route for designing correlated magnetic materials.

Contribution

It introduces a general microscopic mechanism where orbital order driven by correlations leads to 2D metallic altermagnetism with significant spin splitting.

Findings

Monolayer YbMn2Ge2 is a stable correlated metallic altermagnet.

The material exhibits giant nonrelativistic spin splitting of about 1 eV.

The phase supports large, gate-tunable transverse spin conductivity.

Abstract

Two-dimensional metallic altermagnets are rare, and no correlated 2D material has been established to host large nonrelativistic spin splitting. Here we show that spontaneous orbital order, driven by electronic correlations and Fermi surface nesting, provides a general microscopic route to two-dimensional metallic altermagnetism. Antiferro-orbital ordering between the d$_{xz}$ and d$_{yz}$ orbitals breaks the equivalence of magnetic sublattices with opposite spins and generates a symmetry-enforced altermagnetic spin texture. As a concrete realization, we identify monolayer YbMn$_2$Ge$_2$ as a stable correlated metallic altermagnet exhibiting giant nonrelativistic spin splitting of order 1 eV. The resulting phase supports an exceptionally large and gate-tunable transverse spin conductivity. These results establish correlation-driven orbital order as a robust and general mechanism for designing correlated altermagnets with large spin splitting.