Representation-enforced topological nodal planes in hexagonal space groups

Two-dimensional Kramers degeneracies due to twofold screw rotation and time-reversal symmetry, may carry a non-zero Chern number like Weyl points. As a result, for such topological nodal planes Fermi arcs are expected [1]. While the presence of nodal planes in materials is experimentally established [2], a suitable material realization to study their Fermi arcs is still lacking.

In this work we discuss how certain band representations of hexagonal space groups exhibit necessarily topological nodal planes with a charge that cannot be removed, propose material examples and predict their possible surface states. Further, we explain how their topological charge can be estimated using only symmetry eigenvalues and, once time reversal is broken, discuss their signatures in the anomalous Hall and Nernst effects.

[1] Yang, Y., et al., Nat Commun 10, 5185 (2019).

[2] Wilde, Marc A., et al. Nature 594.7863 (2021): 374-379.