Revealing the Underlying Mechanisms of Stacking Order and Interlayer Magnetism in Bilayer CrBr$_3$

TL;DR

This study investigates the stacking configurations and interlayer magnetic interactions in bilayer CrBr3, revealing the dominant Coulomb interactions and exchange mechanisms that govern its magnetic properties, aligning well with recent experimental findings.

Contribution

It provides a detailed analysis of the stacking energy and magnetic interactions in bilayer CrBr3, elucidating the underlying mechanisms and their relation to experimental results.

Findings

Stacking energy mainly determined by Coulomb interactions between interlayer Br atoms.

Interlayer magnetism results from a competition between super-super-exchange and semi-covalent exchange interactions.

Theoretical results agree with recent experimental observations.

Abstract

Aiming to clarify the mechanisms governing the interlayer magnetic coupling, we have investigated the stacking energy and interlayer magnetism of bilayer CrBr$_3$ systemically. The magnetic ground states of bilayer CrBr$_3$ with different R-type and H-type stacking orders are established, which is found to be in good agreement with recent experiment (Science $\mathbf{366}$,983(2019)).Further analyses indicate that the stacking energy is mainly determined by the Coulomb interaction between the interlayer nearest-neighbor Br-Br atoms. While interlayer magnetism can be understood by a competition between super-super-exchange interactions involving $t_{2g}$-$t_{2g}$ and $t_{2g}$-$e_g$ orbitals and semi-covalent exchange interactions of $e_g$-$e_g$ orbitals. Our studies give an insightful understanding for stacking order and interlayer magnetism of bilayer CrBr$_3$, which should be useful to understand quantum confinement effect of other layered magnets in two-dimensional limit.