Fragile Symmetry-Protected Half Metallicity in Two-Dimensional van der Waals Magnets: A Case Study of Monolayer FeCl2

TL;DR

This study investigates the fragility of symmetry-protected half-metallicity in monolayer FeCl2, revealing how electron correlation, spin-orbit coupling, and structural distortions can destroy this property, impacting the design of 2D quantum magnetic materials.

Contribution

It identifies mechanisms that threaten half-metallicity in 2D magnets, emphasizing the importance of considering competing effects in theoretical predictions.

Findings

Symmetry-protected half-metallicity can be destroyed by electron correlation.

Spin-orbit coupling and structural distortions lower the energy and disrupt half-metallicity.

Fragility of half-metallicity impacts the design of 2D spintronic materials.

Abstract

Two-dimensional (2D) half-metallic materials are of great interest for their promising applications in spintronics. Although numerous of 2D half-metals have been proposed theoretically, rarely of them can be synthesized experimentally. Here, exemplified by monolayer FeCl2, we show three mechanisms in such quantum magnets that would cause the metal-insulator transition by using first-principles calculations. In particular, half-metallicity, especially that protected by symmetry-induced degeneracies, predicted by the previous theoretical simulations could be destroyed by electron correlation, spin-orbit coupling and further structural distortions to lower the total energy. Our work reveals the fragility of the symmetry-protected half-metals upon various competing energy-lowering mechanisms, which should be taken into account for theoretically predicting and designing quantum mateirals with exotic functionalities.