  Photo sensing and energy harvesting based on exotic properties of quantum
materials and new operation principles have great potentials to break the
fundamental performance limit of conventional photodetectors and solar cells.
As topological nontrivial materials, Weyl semimetals have demonstrated novel
optoelectronic properties that promise potential applications in photo
detection and energy harvesting arising from their gapless linear dispersion
near Weyl nodes and Berry field enhanced nonlinear optical effect at the
vicinity of Weyl nodes. In this work, we demonstrate robust photocurrent
generation from charge separation of photoexctied electron-hole pairs at the
edge of Td-WTe2, a type-II Weyl semimetal, due to crystalline-symmetry breaking
along certain crystal fracture directions and possibly enhanced by robust
fermi-arc type surface states. Using scanning photocurrent microscopy (SPCM)
measurements, we further demonstrate that the edge current response is robust
over a wide excitation photon energy. We find that this robust feature is
highly generic, and shall arise universally in a wide class of quantum
materials with similar crystal symmetries. In addition, possible connections
between these edge photocurrents and topological properties of Weyl semimetals
are explored. The robust and generic edge current response demonstrated in this
work provides a new type of charge separation mechanism for photosensing and
energy harvesting over broad wavelength range.
