Spin Polarization of Photoelectrons from Topological Insulators
  We show that the degree of spin polarization of photoelectrons from the surface states of topological insulators is 100% if fully-polarized light is used as in typical photoemission measurements, and hence can be significantly "higher" than that of the initial state. Further, the spin orientation of these photoelectrons in general can also be very different from that of the initial surface state and is controlled by the photon polarization; a rich set of predicted phenomena have recently been confirmed by spin- and angle-resolved photoemission experiments. 
Cheol-Hwan Park and Steven G. Louie
cond-mat.mes-hall cond-mat.mtrl-sci