グラフェン中で電子が分数化することを発見(Electrons become fractions of themselves in graphene, study finds)

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2024-02-22 マサチューセッツ工科大学(MIT)

電子は基本的な電気の単位であり、通常、単一の負電荷を運びます。しかし、特殊な物質状態では、電子がその全体の一部に分裂することがあります。これを「分数電荷」と呼び、量子コンピューターの構築に役立つエキゾチックな電子状態が実現する可能性があります。MITの物理学者は、グラフェンの5層でこの分数電荷効果を初めて観測し、これは外部の磁場を必要としないものです。この発見は、基礎物理学にとって重要であり、量子計算のより強力な形態を可能にする可能性があります。

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多層グラフェンにおける分数量子異常ホール効果 Fractional quantum anomalous Hall effect in multilayer graphene

Zhengguang Lu,Tonghang Han,Yuxuan Yao,Aidan P. Reddy,Jixiang Yang,Junseok Seo,Kenji Watanabe,Takashi Taniguchi,Liang Fu & Long Ju
Nature  Published:21 February 2024  DOI:https://doi.org/10.1038/s41586-023-07010-7

グラフェン中で電子が分数化することを発見(Electrons become fractions of themselves in graphene, study finds)

Abstract

The fractional quantum anomalous Hall effect (FQAHE), the analogue of the fractional quantum Hall effect1 at zero magnetic field, is predicted to exist in topological flat bands under spontaneous time-reversal-symmetry breaking2,3,4,5,6. The demonstration of FQAHE could lead to non-Abelian anyons that form the basis of topological quantum computation7,8,9. So far, FQAHE has been observed only in twisted MoTe2 at a moiré filling factor v > 1/2 (refs. 10,11,12,13). Graphene-based moiré superlattices are believed to host FQAHE with the potential advantage of superior material quality and higher electron mobility. Here we report the observation of integer and fractional QAH effects in a rhombohedral pentalayer graphene–hBN moiré superlattice. At zero magnetic field, we observed plateaus of quantized Hall resistance Rxy=ℎ/ve2 at v = 1, 2/3, 3/5, 4/7, 4/9, 3/7 and 2/5 of the moiré superlattice, respectively, accompanied by clear dips in the longitudinal resistance Rxx. Rxy equals 2ℎ/e2 at v = 1/2 and varies linearly with v, similar to the composite Fermi liquid in the half-filled lowest Landau level at high magnetic fields14,15,16. By tuning the gate-displacement field D and v, we observed phase transitions from composite Fermi liquid and FQAH states to other correlated electron states. Our system provides an ideal platform for exploring charge fractionalization and (non-Abelian) anyonic braiding at zero magnetic field7,8,9,17,18,19, especially considering a lateral junction between FQAHE and superconducting regions in the same device20,21,22.

1700応用理学一般
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