  Using Hall photovoltage measurements, we demonstrate that an anomalous
Hall-voltage can be induced in few layer WTe2 under circularly polarized light
illumination. By applying a bias voltage along different crystal axes, we find
that the photo-induced anomalous Hall conductivity coincides with a particular
crystal axis. Our results are consistent with the underlying Berry-curvature
exhibiting a dipolar distribution due to the breaking of crystal inversion
symmetry. Using a time-resolved optoelectronic auto-correlation spectroscopy,
we find that the decay time of the anomalous Hall voltage exceeds the
electron-phonon scattering time by orders of magnitude but is consistent with
the comparatively long spin-lifetime of carriers in the momentum-indirect
electron and hole pockets in WTe2. Our observation suggests, that a helical
modulation of an otherwise isotropic spin-current is the underlying mechanism
of the anomalous Hall effect.
