Recently, the topological nature of an antiferromagnet YbMnBi2 has been controversial. YbMnBi2 is regarded as a candidate of Type-II Weyl semimetals with magnetic moments of Mn atoms canting about 10{\deg} in some studies but as a Dirac semimetal without canting in others. By means of systematical density functional theory calculations, we show the perfect YbMnBi2 bulk has a collinear antiferromagnetic ordering and, naturally, it is a Dirac semimetal. Considering the vital role of magnetic moment canting in generating the Type-II Weyl state, we artificially cant the magnetic moments of Mn atoms and find that YbMnBi2 enters into the Type-II Weyl state from about 2{\deg}. Inspired by this and taking into account the possible defects in experiments, we suggest that Bi vacancies in Mn-Bi-Mn bonds, which produce sizable Dzyaloshinskii-Moriya interactions and thereby cant the magnetic moments of Mn atoms, can tune the topological nature of YbMnBi2 from Dirac semimetals to Type-II Weyl semimetals. Our work unveils the possible underlying mechanism for the Type-II Weyl state in YbMnBi2, providing insights into the Weyl state in other magnetic topological materials.
@article{arxiv.2112.00683,
title = {Origin of the Type-II Weyl state in topological antiferromagnetic YbMnBi2},
author = {Xiao-Sheng Ni and Cui-Qun Chen and Dao-Xin Yao and Yusheng Hou},
journal= {arXiv preprint arXiv:2112.00683},
year = {2022}
}