  One of the hallmarks of light-spin interaction in solids is the appearance of
photocurrent that depends on the light helicity. Recent studies have shown that
helicity dependent photocurrent (HDP) emerges due to light induced spin current
and the inverse spin Hall effect of semimetal thin films. We have studied HDP
in metal/semimetal bilayers. Compared to Bi single layer films, we find the HDP
is enhanced in metal/Bi bilayers. For the bilayers, the sign of HDP under back
illumination reverses from that of front illumination. The back illumination
photocurrent is the largest for Ag/Bi bilayers among the bilayers studied.
Using a diffusive spin transport model, we show that the HDP sign reversal
under back illumination is caused by spin absorption and spin to charge
conversion at the interface. Such interfacial effects contribute to the HDP
enhancement under front illumination for the bilayers when the Bi layer
thickness is small. These results show that the HDP can be used to assess
interface states with strong spin orbit coupling.
