Interchange of Weyl points in the phonon bands of a half-metal alloy

We demonstrate that the topological charge associated with nontrivial phononic Weyl points may be interchanged between nonadjacent locations within the Brillouin zone of a strained crystal. This occurs in our NiMnSb test case upon passing between tensile and compressive uniaxial strain through the higher-symmetry unstrained geometry, and compensates for what would otherwise appear to be nonconservation of topological charge. The phenomenon is dictated by the material's crystallographic point group, and should be replicated in other crystals of similar symmetry. Published by the American Physical Society 2024