Low-temperature crystal and magnetic symmetries in NdBi and the related topological states.*

Recently, ARPES revealed unique surface states below Neel temperature (T_N = 24 K) in face-centered-cubic NdBi [1], characterized by a mix of hole Fermi arc-like features and surface state electron pockets and temperature-dependent band splitting. Density functional theory calculations [2] later showed that multi-q (1q, 2q and 3q) antiferromagnetic structures in the face-centered cubic sublattice of NdBi, can induce the unconventional surface states. The 1q and 2q antiferromagnetic structures have been predicted to host a Dirac semimetals whereas 3q structure is predicted to exhibit Weyl semimetal behavior. To resolve the ambiguity among the possible magnetic structures and determine the corresponding topological state in NdBi, various single-crystal and powder X-ray and neutron diffraction experiments were carried out. Here, we present these results and corresponding analysis of structural and magnetic transitions in NdBi and discuss the low-temperature crystal and magnetic symmetries. 

[1] B. Schrunk, et al. Nature 603, 610 (2022).

[2] LL. Wang, et al. Commun Phys 6, 78 (2023).