Magnetic and electronic structure of the topological semimetal YbMnSb$_2$

TL;DR

This study investigates the magnetic structure of YbMnSb$_2$, revealing a C-type antiferromagnetic order that influences its topological electronic states, with implications for understanding how magnetic arrangements affect topological semimetals.

Contribution

The paper determines the magnetic ground state of YbMnSb$_2$ using neutron diffraction, showing it has a C-type AFM structure that impacts its topological electronic properties.

Findings

Mn moments lie along the c axis

YbMnSb$_2$ has a C-type AFM structure

Gapped Dirac nodes are present near the Fermi level

Abstract

The antiferromagnetic (AFM) semimetal YbMnSb$_2$ 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, $T_\mathrm{N}$ = 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 YbMnSb$_2$ 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.