Fragile symmetry-protected half metallicity in two-dimensional van der Waals magnets: A case study of monolayer <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>Fe</mml:mi><mml:msub><mml:mi>Cl</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>
Qiushi Yao, Jiayu Li, Qihang Liu
Abstract
Two-dimensional (2D) half-metallic materials are of great interest for their promising applications in spintronics. Although numerous 2D half metals have been proposed theoretically, rarely can they be synthesized experimentally. Here, exemplified by monolayer $\mathrm{Fe}{\mathrm{Cl}}_{2}$, 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 materials with exotic functionalities.