Nano-photocurrent Mapping of Local Electronic Structure in Twisted Bilayer Graphene
Sai Sunku, Alexander McLeod, Tobias Stauber, Hyobin Yoo, Dorri Halbertal, Guangxin Ni, Aaron Sternbach, Bor‐Yuan Jiang, Takashi Taniguchi, Kenji Watanabe, Philip Kim, M. M. Fogler, D. N. Basov
Abstract
We report a combined nano-photocurrent and infrared nanoscopy study of twisted bilayer graphene (TBG) enabling access to the local electronic phenomena at length scales as short as 20 nm. We show that the photocurrent changes sign at carrier densities tracking the local superlattice density of states of TBG. We use this property to identify domains of varying local twist angle by local photothermoelectric effect. Consistent with the photocurrent study, infrared nanoimaging experiments reveal optical conductivity features dominated by twist-angle-dependent interband transitions. Our results provide a fast and robust method for mapping the electronic structure of TBG and suggest that similar methods can be broadly applied to probe electronic inhomogeneities of Moiré superlattices in other van der Waals heterostructures.