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The electronic properties of moiré heterostructures depend sensitively on the relative orientation between layers of the stack. As one example, near-magic-angle twisted bilayer graphene (TBG) commonly shows superconductivity, yet a TBG sample where one of the graphene layers was rotationally aligned to a hexagonal Boron Nitride (hBN) cladding layer instead provided the first experimental observation of orbital ferromagnetism. To create samples with aligned graphene/hBN, researchers often align edges of exfoliated flakes that appear straight in optical micrographs. However, graphene or hBN can cleave along either zig-zag or armchair lattice directions, introducing a 30◦ ambiguity in the relative orientation of two flakes. By characterizing the crystal lattice orientation of exfoliated flakes prior to stacking using Raman and second-harmonic generation for graphene and hBN, respectively, we can now unambiguously align monolayer graphene to hBN at a near-0◦, not 30◦, relative twist angle. We confirm this alignment by torsional force microscopy (TFM) of the graphene/hBN moiré on an open-face stack, and then by cryogenic transport measurements, after full encapsulation with a second, non-aligned hBN layer. This work demonstrates a key step toward systematically exploring the effects of the relative twist angle between dissimilar materials within moiré heterostructures.

権利情報:

• Creative Commons BY Attribution 4.0 International
  

キーワード: Moiré heterostructures, graphene, hBN cladding

刊行年月日: 2024-09-27

出版者: Proceedings of the National Academy of Sciences

掲載誌:

• Proceedings of the National Academy of Sciences (ISSN: 00278424) vol. 121 issue. 40

研究助成金:

• Gordon and Betty Moore Foundation GBMF9460
• JSPS KAKENHI 21H05233
• JSPS KAKENHI 23H02052
• DOE | Office of Science DE-AC02-76SF00515
• DOE | Office of Science DE-AC02-76SF00515
• National Science Foundation ECCS-2026822

原稿種別: 出版者版 (Version of record)

MDR DOI:

公開URL: https://doi.org/10.1073/pnas.2410993121

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更新時刻: 2025-02-05 12:31:29 +0900

MDRでの公開時刻: 2025-02-05 12:31:29 +0900