Hyperbolic enhancement of photocurrent patterns in minimally twisted bilayer graphene

Quasi-periodic moire patterns and their effect on electronic properties of twisted bilayer graphene have been intensely studied. At small twist angle theta, due to atomic reconstruction, the moire superlattice morphs into a network of narrow domain walls separating micron-scale AB and BA stacking regions. We use scanning probe photocurrent imaging to resolve nanoscale variations of the Seebeck coefficient occurring at these domain walls. The observed features become enhanced in a range of mid-infrared frequencies where the hexagonal boron nitride substrate is optically hyperbolic. Our results illustrate the capabilities of the nano-photocurrent technique for probing nanoscale electronic inhomogeneities in two-dimensional materials. Here, the authors use scanning probe photocurrent imaging to resolve nanoscale variations of the Seebeck coefficient occurring at domain walls separating micron-scale AB and BA stacking regions in twisted bilayer graphene, and observe hyperbolic enhancement of the photocurrent pattern.

Automated summary

The study focuses on quasi-periodic moire patterns and their impact on electronic properties of twisted bilayer graphene. Using scanning probe photocurrent imaging, nanoscale variations of the Seebeck coefficient at domain walls separating stacking regions are resolved, with an observed hyperbolic enhancement of the photocurrent pattern in the mid-infrared frequency range. This illustrates the ability of nano-photocurrent technique to probe nanoscale electronic inhomogeneities in two-dimensional materials.