Photonic spin Hall effect on the surfaces of type-I and type-II Weyl semimetals

Topological optics is an emerging research area in which various topological and geometrical ideas are being proposed to design and manipulate the behaviors of photons. Here, the photonic spin Hall effect on the surfaces of topological Weyl semimetal (WSM) films was studied. Our results show that the spin-dependent splitting (i.e. photonic spin Hall shifts) induced by the spin-orbit interaction is little sensitive to the tilt αt of Weyl nodes and the chemical potential μ in type-I WSM film. In contrast, photonic spin Hall shifts in both the in-plane and transverse directions present versatile dependent behaviors on the αt and μ in type-II WSM film. In particular, the largest in-plane and transverse spin Hall shifts appear at the tilts between −2 and −3, which are ~40 and ~10 times of the incident wavelength, respectively. Nevertheless, the largest spin Hall shifts for type-II WSM film with positive αt are only several times of incident wavelength. Moreover, the photonic spin Hall shifts also exhibit different variation trends with decreasing the chemical potential for different signs of αt in type-II WSM films. This dependence of photonic spin Hall shifts on tilt orientation in type-II WSM films has been explained by time-reversal-symmetry-breaking Hall conductivities in WSMs.