  Dirac semimetals are expected to forbid the manifestation of the circular
photogalvanic effect (CPGE) because of their crystal inversion symmetry. Here,
we report the observation of the CPGE in Cd3As2 nanobelt field effect
transistors, when the photoexcitation is focused in the vicinity of the metal
contacts up to room temperature. We attribute the CPGE to the Schottky electric
field induced symmetry breaking, which results in the photocurrent modulation
by circularly polarized photoexcitation via spin-momentum locking. The
hypothesis is supported by a suite of experiments including spatially and
angularly resolved helicity dependent photocurrent, Kelvin probe force
microscopy, and gate voltage dependence. First principles calculations
confirmed a topological phase transition upon field induced structural
distortion. This work provides key insights on the electrically controlled
helicity dependent optoelectronics in Dirac materials.
