  The intrinsic spin-orbit coupling in the 2D staggered monolayer
semiconductors is very large as compared to graphene. The large spin orbit
interaction in these materials leads to the opening of a gap in the energy
spectrum and spin-splitting of the bands in each valley. In this paper, we
theoretically investigate the mechanical steering of beams from these
spin-orbit rich, staggered 2D materials. Mechanical steering results in
noticeable deviations of the reflected and transmitted ray profiles as
predicted from classical laws of optics. These effects are generally called the
Goos-Hanchen (GH) and Imbert-Fedorov shifts. We find that electric and magnetic
field modulated giant spatial and angular GH shifts can be achieved in these
materials for incident angles in the vicinity of Brewster angle in terahertz
regime. We also determine the dependence of beam shifts on the chemical
potential and find that the Brewster angle and the sign of GH shift can be
controlled by varying the chemical potential. This allows the possibility of
realizing spin and valley dependent optical effects that can be useful readout
markers for experiments in quantum information processing, biosensing and
valleytronics, employed in the terahertz regime.
