Spin Wave Effects in Transport between a Ferromagnet and a Weyl Semimetal Surface

We experimentally investigate spin-polarized transport between a ferromagnetic Ni electrode and a surface of Weyl semimetal, realized in a thick WTe2 single crystal. For highly transparent Ni-WTe2 planar junctions, we observe non-Ohmic dV/dI (I) behavior with an overall increase in differential resistance dV/dI with current bias, which is accomplished by peaks and dips structures. This behavior is inconsistent with trivial interface scattering, but it is well known for spin-polarized transport with magnon emission. Thus, we interpret the experimental results in terms of spin wave excitation in spin textures in the WTe2 topological surface states, which is supported by the obtained magnetic field and temperature dependences of dV/dI (I).