Three-dimensional zigzag correlations in the van der Waals Kitaev magnet RuBr$_3$

TL;DR

This study reveals that RuBr₃ exhibits persistent three-dimensional zigzag magnetic correlations above its Ne9el temperature, driven by interlayer interactions, highlighting its distinct magnetic behavior among Ru-based van der Waals materials.

Contribution

The paper uncovers the presence of three-dimensional zigzag correlations in RuBr₃ above T_N, emphasizing the role of interlayer interactions mediated by Br orbitals in stabilizing these correlations.

Findings

Zigzag correlations persist above T_N in RuBr₃.

Interlayer magnetic interactions are enhanced by Br 4p orbitals.

Spectral weight redistribution indicates 3D zigzag correlations.

Abstract

Ruthenium trihalides Ru$X_3$ ($X$ = Cl, Br, I) provide a tunable platform for Kitaev magnetism in two-dimensional van der Waals materials. Despite their similar crystal structures and zigzag antiferromagnetic order, RuBr$_3$ exhibits a higher N\'eel temperature ($T_N$) than RuCl$_3$, suggesting their distinct proximity to the Kitaev quantum spin liquid phase. Using Ru $L_3$-edge resonant x-ray scattering, we show that, while the long-range zigzag order in RuBr$_3$ disappears at $T_N$, the zigzag correlations that persist well above $T_N$ show a pronounced spectral weight redistribution along the interlayer direction. These results suggest that the enhanced interlayer magnetic interactions driven by the extended Br 4$p$ orbitals stabilize three-dimensional zigzag correlations in RuBr$_3$.