From triple points to multi-band nodal links with monopole charges*

We use non-Abelian topology to derive a relation between seemingly unrelated band node configurations. Namely, we show that rotation-symmetry breaking converts certain triple nodal points into multi-band nodal links. To derive this relation, we first classify triple points in PT-symmetric systems with negligible spin-orbit coupling, and then use quaternion invariants to identify the symmetry criteria which ensure the described conversion.
Based on the above, I will outline several further implications of triple-point configurations. These are, in particular, non-trivial Euler and Stiefel-Whitney monopole charges, which may facilitate higher-order topology with hinge charges. Finally, I will present triple-point material candidates, identified via first-principles calculations, which we predict to exhibit the described physics under the application of a symmetry-breaking strain.