  Conventional photocurrents at a p-n junction depend on macroscopic built-in
fields and are typically insensitive to the microscopic details of a crystal's
atomic configuration. Here we demonstrate how atomic configuration can control
photocurrent in van der Waals (vdW) materials. In particular, we find bulk
shift photocurrents (SPC) can display a rich (atomic) configuration dependent
phenomenology that range from contrasting SPC currents for different stacking
arrangements in a vdW homostructure (e.g., AB vs BA stacking) to a strong light
polarization dependence for SPC that align with crystallographic axes.
Strikingly, we find that SPC in vdW homostructures can be directed by modest
strain, yielding sizeable photocurrent magnitudes under unpolarized light
irradiation and manifesting even in the absence of p-n junctions. These
demonstrate that SPC are intimately linked to how the Bloch wavefunctions are
embedded in real space, and enables a new macroscopic transport probe
(photocurrent) of lattice-scale registration in vdW materials.
