Tunable Topological Transitions Probed by the Quantum Hall Effect in Twisted Double Bilayer Graphene,Nano Letters

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Tunable Topological Transitions Probed by the Quantum Hall Effect in Twisted Double Bilayer Graphene
Nano Letters ( IF 9.6 ) Pub Date : 2024-12-20 , DOI: 10.1021/acs.nanolett.4c04242
Zehao Jia ₁ , Xiangyu Cao ₁ , Shihao Zhang _{2,

3,

4} , Jinshan Yang ₅ , Jingyi Yan ₅ , Yuda Zhang ₁ , Xin Lu ₃ , Pengliang Leng ₁ , Enze Zhang ₁ , Linfeng Ai ₁ , Xiaoyi Xie ₁ , Minsheng Li ₁ , Li Qian ₁ , Jianpeng Liu _{3,

4} , Shaoming Dong ₅ , Faxian Xiu _{1,

6,

7,

8}

Affiliation

The moiré system provides a tunable platform for investigating exotic quantum phases. Particularly, the displacement field D is crucial for tuning the electronic structures and topological properties of twisted double bilayer graphene (TDBG). Here, we present a series of D-tunable topological transitions by the evolution of quantum Hall phases (QHPs) in the valence bands of TDBG. As D increases, we observe the alternating emergence of two distinct quantum Hall regions originating from full-filling and half-filling, which we attribute to the D-induced Lifshitz transition. Moreover, we delve into the remote valence bands of TDBG and observe a transition in the sequence of Landau levels upon the application of D, shifting from 8N + 4 to 8N. This observation, combined with theoretical calculations, unveils an alteration in the Berry phase. Our findings highlight the TDBG as an exemplary platform for understanding the origin of the topological transitions in the graphene-based moiré systems.

中文翻译：

扭曲双层石墨烯中量子霍尔效应探测的可调谐拓扑跃迁

莫尔系统为研究奇异量子相位提供了一个可调平台。特别是，位移场 D 对于调整扭曲双层石墨烯（TDBG）的电子结构和拓扑特性至关重要。在这里，我们通过量子霍尔相（QHP）在 TDBG 的价带中的演变提出了一系列 D 可调拓扑跃迁。随着 D 的增加，我们观察到两个不同的量子霍尔区域交替出现，这些区域起源于完全填充和半填充，我们将其归因于 D 诱导的 Lifshitz 跃迁。此外，我们深入研究了 TDBG 的远程价带，并观察到在应用 D 时朗道能级序列的转变，从 8N + 4 转变为 8N。这一观察结果与理论计算相结合，揭示了 Berry 相的变化。我们的研究结果突出了 TDBG 是理解基于石墨烯的莫尔系统中拓扑转变起源的示例平台。

更新日期：2024-12-20

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