Neutron Scattering Signatures of Magnon Weyl Points

Understand

We study the inelastic neutron scattering cross section in the vicinity of touching points in magnon bands.

• Among the possible touching points are magnon Weyl points in three dimensional ordered magnets with significant spin-orbit coupling that are characterized by a linear dispersion in their vicinity.
• A Weyl point is topologically protected by its net chirality and here we show that this leads to a characteristic form for the dynamical structure factor.
• To address this question, we show that scattering intensities in the vicinity of arbitrary magnon two-band touching points are identical to expectation values of the pseudospin polarization along some direction $\hat{\boldsymbol{n}}$ in momentum space fixed by the magnetic Hamiltonian.