Nonsymmorphic-symmetry-protected topological magnons in three-dimensional Kitaev materials

Topological phases in magnetic materials offer novel tunability of topological properties through varying the underlying magnetism. We show that field-induced canted zig-zag order of three-dimensional hyperhoneycomb Kitaev materials has gapless topological magnons protected by nonsymmorphic magnetic space group symmetries. The non-Hermitian nature of the bosonic magnons leads to unique topological protection that is different from their fermionic counterparts. We investigate how such topological magnons can be controlled by varying the strength of the spin-exchange interactions.