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Recently, magic-angle twisted bilayer graphene (MATBLG) has shown the emergence of various interaction-driven novel quantum phases at the commensurate fillings of the moire ́ superlattice, while the charge neutrality point (CNP) remains mostly a vanilla insulator. Here, we show an emerging phase of nearly compensated semimetallicity at the CNP of twisted double bilayer graphene (TDBLG), a close cousin of MATBLG, with a signature of strong correlation. Using electrical and thermal transport, we find almost two orders of magnitude enhancement of the thermopower in magnetic fields much smaller than the extreme quantum limit, accompanied by a large magnetore- sistance (∼ 2500%) at CNP. This provides indisputable experimental evidence that TDBLG near CNP is a compensated semimetal. Moreover, we observe a two-peak structure in the resistance variation with carrier density around the CNP and its unusual sublinear temperature dependence at low temperatures. The electronic correlations determine the fate of the co-existing small electron and hole pockets near the CNP of the semimetallic TDBLG. Our theory with the formation of excitonic metal explains the resistance feature and its unique sublinear temperature dependence.

権利情報:

• Creative Commons BY Attribution 4.0 International
  

キーワード: Magic-angle twisted bilayer graphene, compensated semimetallicity, electronic correlation

刊行年月日: 2023-12-16

出版者: Springer Science and Business Media LLC

掲載誌:

• Communications Physics (ISSN: 23993650) vol. 6 issue. 1 360

研究助成金:

• Department of Science and Technology, Ministry of Science and Technology
• DST | Science and Engineering Research Board

原稿種別: 出版者版 (Version of record)

MDR DOI:

公開URL: https://doi.org/10.1038/s42005-023-01480-x

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更新時刻: 2025-02-26 12:30:33 +0900

MDRでの公開時刻: 2025-02-26 12:30:33 +0900