  In this paper we theoretically investigate the photonic spin Hall effect
(SHE) of a Gaussian beam reflected from the interface between air and
topological insulators (TIs). The photonic SHE is attributed to spin-orbit
coupling and manifests itself as in-plane and transverse spin-dependent
splitting. We reveal that the spin-orbit coupling effect in TIs can be routed
by adjusting the axion angle variations. Unlike the transverse spin-dependent
splitting, we find that the in-plane one is sensitive to the axion angle. It is
shown that the polarization structure in magneto-optical Kerr effect is
significantly altered due to the spin-dependent splitting in photonic SHE. We
theoretically propose a weak measurement method to determine the strength of
axion coupling by probing the in-plane splitting of photonic SHE.
