Observation of a chiral wave function in the twofold-degenerate quadruple Weyl system BaPtGe

Topological states in quantum materials are defined by bulk wave functions that possess nontrivial topological invariants. While edge modes widely presented as signatures of topology, how can manifest explicitly properties remains unresolved. Here, using high-resolution inelastic x-ray spectroscopy (IXS) combined with first principles calculations, we report experimental chiral the phonon spectrum BaPtGe, which show to host a previously undiscovered twofold-degenerate quadruple Weyl node. The chirality degenerate phononic function yields dynamical structure factor, $S(\mathbf{Q},\ensuremath{\omega})$, along high-symmetry directions, is excellent agreement numerical and model calculations. Our results establish IXS powerful tool uncover functions, providing key missing ingredient study matter.