  Spin- and angle-resolved photoemission spectroscopy is used to reveal that a
large spin polarization is observable in the bulk centrosymmetric transition
metal dichalcogenide MoS2. It is found that the measured spin polarization can
be reversed by changing the handedness of incident circularly-polarized light.
Calculations based on a three-step model of photoemission show that the valley
and layer-locked spin-polarized electronic states can be selectively addressed
by circularly-polarized light, therefore providing a novel route to probe these
hidden spin-polarized states in inversion-symmetric systems as predicted by
Zhang et al. [Nature Physics 10, 387 (2014)].
