Hyperbolic enhancement of photocurrent patterns in minimally twisted bilayer graphene

TL;DR

This study uses scanning probe photocurrent imaging to reveal enhanced nanoscale electronic variations at domain walls in twisted bilayer graphene, especially under hyperbolic conditions of the substrate, demonstrating new probing capabilities.

Contribution

It introduces a novel application of nano-photocurrent imaging to resolve nanoscale electronic inhomogeneities in twisted bilayer graphene with hyperbolic substrate effects.

Findings

Enhanced photocurrent features at domain walls in TBG.

Nanoscale Seebeck coefficient variations detected.

Hyperbolic hBN substrate amplifies photocurrent signals.

Abstract

Quasi-periodic moir\'{e} patterns and their effect on electronic properties of twisted bilayer graphene (TBG) have been intensely studied. At small twist angle $\theta$, due to atomic reconstruction, the moir\'e 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 (hBN), which we use as a TBG substrate, is optically hyperbolic. Our results illustrate new capabilities of nano-photocurrent technique for probing nanoscale electronic inhomogeneities in two-dimensional materials.