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Twist-controlled moiré superlattices (MS) have emerged as a versatile platform for realizing artificial systems with complex electronic spectra. The combination of Bernal-stacked bilayer graphene (BLG) and hexagonal boron nitride (hBN) can give rise to an interesting MS, that has recently featured a set of unexpected behaviors, such as unconventional ferroelectricity and the electronic ratchet effect. Yet, the understanding of the electronic properties of BLG/hBN MS has, at present, remained fairly limited. Here, we combine magneto-transport and low-energy sub-THz excitation to gain insights into the properties of this MS. We demonstrate that the alignment between BLG and hBN
crystal lattices results in the emergence of compensated semimetals at some integer fillings of the moiré bands, separated by van Hove singularities where Lifshitz transition occurs. A particularly pronounced semimetal develops when eight holes reside in the moiré unit cell, where coexisting high-mobility electron and hole systems feature strong magnetoresistance reaching 2350% already at B = 0.25 T. Next, by measuring the THz-driven Nernst effect in remote bands, we observe valley splitting, indicating an orbital magnetization characterized by a strongly enhanced effective g_v-factor of 340. Finally, using THz photoresistance measurements, we show that the high-temperature conductivity of the BLG/hBN MS is limited by electron-electron umklapp processes. Our multi-faceted analysis introduces THz-driven magnetotransport as a convenient tool to probe the band structure and interaction effects in van der Waals materials and provides a comprehensive understanding of the BLG/hBN MS.

権利情報:

• In Copyright
  This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Nano, copyright © 2024 American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acsnano.3c13212.

キーワード: Moiré Superlattices, Bilayer Graphene, Orbital Magnetization, Compensated Semimetals, Umklapp Scattering, Terahertz

刊行年月日: 2024-05-07

出版者: American Chemical Society (ACS)

掲載誌:

• ACS Nano (ISSN: 1936086X) vol. 18 issue. 8 p. 11769-11777

研究助成金:

• Ministerio de Ciencia e Innovaci?n PID2022-142162NB-I00
• European Regional Development Fund
• H2020 Marie Sklodowska-Curie Actions 101034431
• Japan Society for the Promotion of Science 20H00354
• Japan Society for the Promotion of Science 21H05233
• Japan Society for the Promotion of Science 23H02052
• Graphene Flagship
• Lloyd Register Foundation
• Center for Neurophysics and Neuromorphic Technologies
• Engineering and Physical Sciences Research Council EP/S030719/1
• Engineering and Physical Sciences Research Council EP/V007033/1
• Royal Society RSRP\R\190000
• European Commission
• Agency for Science, Technology and Research M22K3c0106
• Ministry of Education, Culture, Sports, Science and Technology
• Ministry of Education - Singapore EDUNC-33-18-279-V12
• Ministry of Education - Singapore T2EP50123-0020
• Ministerio de Ciencia e Innovaci?n CEX2020-001039-S/AEI/10.13039/501100011033

原稿種別: 著者最終稿 (Accepted manuscript)

MDR DOI:

公開URL: https://doi.org/10.1021/acsnano.3c13212

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更新時刻: 2025-07-29 12:30:20 +0900

MDRでの公開時刻: 2025-07-29 12:21:26 +0900