Chiral anomaly of Weyl magnons in stacked honeycomb ferromagnets

One of the most important signatures of Weyl materials is the chiral anomaly. So far, there has been little study of chiral anomaly of Weyl magnons, featured by nontrivial band crossings at paired Weyl nodes of opposite chirality, while the anomaly for its electronic counterpart can routinely be observed in experiments. Here a road map for realizing and detecting the chiral anomaly of Weyl magnons in stacked honeycomb ferromagnets that are shown to be a Weyl magnetic material is provided. Using the Aharonov-Casher effect that is about the interaction between magnetic moments and electric fields, the magnon motion in honeycomb ferromagnetic layers can be quantized into magnonic Landau levels by a proper inhomogeneous electric field. The zeroth magnonic Landau level is chiral so that, under a magnetic field gradient, Weyl magnons propagate unidirectionally from one Weyl node to the other and reverse their chiralities, resulting in the magnonic chiral anomaly. A net magnon current carrying spin and heat through the zeroth magnonic Landau level depends linearly on the magnetic field gradient and the electric field gradient in the linear transport region. The linear spin and heat conductance can serve as the signatures of magnonic chiral anomaly. Furthermore, an experimental realization is proposed.