  The electronic wavefunctions in moir\'e materials are highly sensitive to the
details of the local atomic configuration enabling Bloch band geometry and
topology to be controlled by stacking and strain. Here we predict that large
injection currents (under circular polarized irradiation) can develop in
strained twisted bilayer graphene (TBG) heterostructures with broken sublattice
symmetry; such bulk photovoltaic currents flow even in the absence of a p-n
junction and can be controlled by the helicity of incident light. As we argue,
large injection current rates proceed from strong and highly peaked interband
Berry curvature dipole distributions (arising from the texturing of Bloch
wavefunctions in strained TBG heterostructures). Strikingly, we find that TBG
injection current displays pronounced responses in the THz regime and can be
tuned by chemical potential. These render injection currents a useful
photocurrent probe of symmetry breaking in TBG heterostructures and make TBG a
promising material for THz technology.
