Topological semimetals in ferromagnetic materials have attracted enormous attention due to the potential applications in spintronics. Using the first-principles density functional theory together with an effective lattice model, here we present a new family of topological semimetals with a fully spin-polarized nodal loop in alkaline-metal monochalcogenide MX (M = Li, Na, K, Rb, Cs; X = S, Se, Te) monolayers. The half-metallic ferromagnetism can be established in MX monolayers, in which one nodal loop formed by two crossing bands with the same spin components is found at the Fermi energy. This nodal loop half-metal survives even when considering the spin-orbit coupling owing to the symmetry protection provided by the Mz mirror plane. The quantum anomalous Hall state and Weyl-like semimetal in this system can be also achieved by rotating the spin from the out-of-plane to the in-plane direction. The MX monolayers hosting rich topological phases thus offer an excellent materials platform for realizing the advanced spintronics concepts.
@article{arxiv.1903.11025,
title = {Fully spin-polarized nodal loop semimetals in alkaline-metal monochalcogenide monolayers},
author = {Xiaodong Zhou and Run-Wu Zhang and Zeying Zhang and Da-Shuai Ma and Wanxiang Feng and Yuriy Mokrousov and Yugui Yao},
journal= {arXiv preprint arXiv:1903.11025},
year = {2019}
}