  In three-dimensional (3D) quantum magnets, magnonic Weyl points (WPs)
featuring linear band crossing of two non-degenerate magnon branches can emerge
in certain lattice geometry when time-reversal symmetry is broken
macroscopically. Unfortunately, there are very limited 3D quantum magnets that
host magnonic WPs, and they are yet to be observed experimentally because the
intrinsic perturbative interactions that break time-reversal symmetry
macroscopically can be very negligible. Here, we present an alternative means
via photo-irradiation, in which magnonic WPs can emerge in 3D quantum magnets
without relying on intrinsic perturbative interactions to break time-reversal
symmetry. By utilizing the magnonic Floquet-Bloch theory, we put forward the
general theory of magnonic Floquet WPs in 3D quantum magnets. We show that
periodically driven 3D magnonic Dirac nodal-line (DNL) and 3D magnonic gapped
trivial insulators can generate 3D magnonic Floquet WPs, which can be tuned by
the incident circularly-polarized light. We demonstrate the existence of
magnonic Floquet WPs by combining the study of the magnon dispersions, Berry
curvatures, and the anomalous thermal Hall effect. The general theoretical
formalism can be applied to different magnetic insulators, and thus extending
the concept of magnonic WPs to a broader class of 3D magnetically ordered
systems.
