Nano-imaging photoresponse in a moiré unit cell of minimally twisted bilayer graphene

Niels C. H. Hesp, Iacopo Torre, David Barcons-Ruiz, Hanan Herzig Sheinfux, Kenji Watanabe, Takashi Taniguchi, Roshan Krishna Kumar () and Frank H. L. Koppens ()
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Niels C. H. Hesp: ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology
Iacopo Torre: ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology
David Barcons-Ruiz: ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology
Hanan Herzig Sheinfux: ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology
Kenji Watanabe: National Institute for Materials Science
Takashi Taniguchi: National Institute for Materials Science
Roshan Krishna Kumar: ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology
Frank H. L. Koppens: ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology

Nature Communications, 2021, vol. 12, issue 1, 1-8

Abstract: Abstract Graphene-based moiré superlattices have recently emerged as a unique class of tuneable solid-state systems that exhibit significant optoelectronic activity. Local probing at length scales of the superlattice should provide deeper insight into the microscopic mechanisms of photoresponse and the exact role of the moiré lattice. Here, we employ a nanoscale probe to study photoresponse within a single moiré unit cell of minimally twisted bilayer graphene. Our measurements reveal a spatially rich photoresponse, whose sign and magnitude are governed by the fine structure of the moiré lattice and its orientation with respect to measurement contacts. This results in a strong directional effect and a striking spatial dependence of the gate-voltage response within the moiré domains. The spatial profile and carrier-density dependence of the measured photocurrent point towards a photo-thermoelectric induced response that is further corroborated by good agreement with numerical simulations. Our work shows sub-diffraction photocurrent spectroscopy is an exceptional tool for uncovering the optoelectronic properties of moiré superlattices.

Date: 2021
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DOI: 10.1038/s41467-021-21862-5

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