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説明:

Determining the symmetry breaking order of correlated quantum phases is essential for under- standing the microscopic interactions in their host systems. The flat bands in magic-angle twisted bilayer graphene (MATBG) provide an especially rich arena to investigate such interaction- driven ground states, and while progress has been made in identifying the correlated insulators and their excitations at commensurate moir ́e filling factors, the spin-valley polarization of the Chern insulators that emerge at high fields remains unknown. Here we intro- duce a new technique based on twist-decoupled van der Waals layers that enables measurements of their chemical potentials and, by studying the backscattering between counter-propagating edge states, determination of their relative spin polarization. Applying this method to twist-decoupled MATBG and monolayer graphene, we find that the quantum Hall states near the charge neutrality point in MATBG favor spin-unpolarized states at even integer filling factors. The measurements also indicate that the correlated Chern insulator emerging from half filling of the flat valence band is spin-unpolarized, but suggest that its conduction band counterpart may be spin-polarized. Our results constrain models of spin-valley ordering in MATBG and establish a versatile approach to study the electronic properties of van der Waals systems.

権利情報:

• Creative Commons BY Attribution 4.0 International
  

キーワード: Magic-angle twisted bilayer graphene, spin-valley polarizations, quantum Hall states

刊行年月日: 2024-05-21

出版者: Springer Science and Business Media LLC

掲載誌:

• Nature Communications (ISSN: 20411723) vol. 15 issue. 1 4321

研究助成金:

• U.S. Department of Energy DE-SC0021238

原稿種別: 出版者版 (Version of record)

MDR DOI:

公開URL: https://doi.org/10.1038/s41467-024-48385-z

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更新時刻: 2025-02-07 16:30:33 +0900

MDRでの公開時刻: 2025-02-07 16:30:33 +0900