Cryogenic nano-imaging of second-order moiré superlattices.

Autor: Hesp NCH; ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels, Spain., Batlle-Porro S; ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels, Spain., Krishna Kumar R; ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels, Spain., Agarwal H; ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels, Spain., Barcons Ruiz D; ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels, Spain., Herzig Sheinfux H; ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels, Spain., Watanabe K; Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan., Taniguchi T; International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan., Stepanov P; ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels, Spain. pstepano@nd.edu.; Department of Physics and Astronomy, University of Notre Dame, Notre Dame, IN, USA. pstepano@nd.edu.; Stavropoulos Center for Complex Quantum Matter, University of Notre Dame, Notre Dame, IN, USA. pstepano@nd.edu., Koppens FHL; ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels, Spain. frank.koppens@icfo.eu.; ICREA-Institució Catalana de Recerca i Estudis Avançats, Barcelona, Spain. frank.koppens@icfo.eu.
Jazyk: angličtina
Zdroj: Nature materials [Nat Mater] 2024 Sep 10. Date of Electronic Publication: 2024 Sep 10.
DOI: 10.1038/s41563-024-01993-y
Abstrakt: Second-order superlattices form when moiré superlattices with similar periodicities interfere with each other, leading to larger superlattice periodicities. These crystalline structures are engineered using two-dimensional materials such as graphene and hexagonal boron nitride, and the specific alignment plays a crucial role in facilitating correlation-driven topological phases. Signatures of second-order superlattices have been identified in magnetotransport experiments; however, real-space visualization is still lacking. Here we reveal the second-order superlattice in magic-angle twisted bilayer graphene closely aligned with hexagonal boron nitride through electronic transport measurements and cryogenic nanoscale photovoltage measurements and evidenced by long-range periodic photovoltage modulations. Our results show that even minuscule strain and twist-angle variations as small as 0.01° can lead to drastic changes in the second-order superlattice structure. Our real-space observations, therefore, serve as a 'magnifying glass' for strain and twist angle and can elucidate the mechanisms responsible for the breaking of spatial symmetries in twisted bilayer graphene.
(© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)
Databáze: MEDLINE
Externí odkaz: