Abstract
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 (SPCs) 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.
Highlights
The atomic scale registration formed when two van der Waals layers are stacked on top of each other can have a profound influence on its electronic behaviour1,2
We find bulk shift photocurrents (SPC) can display a rich configuration dependent phenomenology that range from contrasting SPC currents for different stacking arrangements in a van der Waals (vdW) homostructure (e.g., are related by (AB) vs BA stacking) to a strong light polarization dependence for SPC that align with crystallographic axes
These demonstrate that SPC are intimately linked to how the Bloch wavefunctions are embedded in real space, and enables a new macroscopic transport probe of lattice-scale registration in vdW materials
Summary
I. Symmetry and Stacking Analysis of Shift Vector in van der Waals materials and homostructures. We present the shift vector dependence on the symmetry and stacking arrangement in van der Waals (vdW) materials and homostructures. We show that the shift vector is highly sensitive to the local atomic configuration of the structure, leading to stacking and polarisation dependent SPC. For our symmetry and stacking analysis below, it will be useful to re-express this conventional form of the shift vector in terms of a Wilson line: r(θ, k) = lim ∇q arg[W(θ, k, q)],. We examine the properties of un(k)|um(q) and un(k)|νθ|um(q) in different vdW materials and homostructures and the atomic configuration dependence of the shift vector and SPC. We illustrate the configuration dependent SPC in Bernal stacked bilayer graphene (BLG), graphene on hexagonal boron nitride (G/hBN), monolayer transition metal dicalcogenide (TMD) and 2H stacked bilayer TMD
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