The antiferromagnetic (AFM) semimetal YbMnSb2 has recently been identified as a candidate topological material, driven by time-reversal symmetry breaking. Depending on the ordered arrangement of Mn spins below the N\'{e}el temperature, TN = 345 K, the electronic bands near the Fermi energy can ether have a Dirac node, a Weyl node or a nodal line. We have investigated the ground state magnetic structure of YbMnSb2 using unpolarized and polarized single crystal neutron diffraction. We find that the Mn moments lie along the c axis of the P4/nmm space group and are arranged in a C-type AFM structure, which implies the existence of gapped Dirac nodes near the Fermi level. The results highlight how different magnetic structures can critically affect the topological nature of fermions in semimetals.
@article{arxiv.2107.02857,
title = {Magnetic and electronic structure of the topological semimetal YbMnSb$_2$},
author = {Jian-Rui Soh and Siobhan M. Tobin and Hao Su and Ivica Zivkovic and Bachir Ouladdiaf and Anne Stunault and J. Alberto Rodríguez-Velamazán and Ketty Beauvois and Yanfeng Guo and Andrew T. Boothroyd},
journal= {arXiv preprint arXiv:2107.02857},
year = {2021}
}