Switchable Chern insulator, isospin competitions and charge density waves in rhombohedral graphene moire superlattices

Jian Zheng; Size Wu; Kai Liu; Bosai Lyu; Shuhan Liu; Yating Sha; Zhengxian Li; Kenji Watanabe; Takashi Taniguchi; Jinfeng Jia; Zhiwen Shi; Guorui Chen

arXiv · 2412.09985

Switchable Chern insulator, isospin competitions and charge density waves in rhombohedral graphene moire superlattices

Jian Zheng·Size Wu·Kai Liu·Bosai Lyu·Shuhan Liu·Yating Sha·Zhengxian Li·Kenji Watanabe·Takashi Taniguchi·Jinfeng Jia·Zhiwen Shi·Guorui Chen

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Abstract

Graphene-based moire superlattices provide a versatile platform for exploring novel correlated and topological electronic states, driven by enhanced Coulomb interactions within flat bands. The intrinsic tunability of graphene s multiple degrees of freedom enables precise control over these complex quantum phases. In this study, we observe a range of competing phases and their transitions in rhombohedrally stacked hexalayer graphene on hexagonal boron nitride (r-6G/hBN) moire superlattices. When electrons are polarized away from the moire superlattice, we firstly identify a Chern insulator with reversible Chern numbers at v = 1 (one electron per moire cell), attributed to the competition between bulk and edge magnetizations.Then, we detect transitions between three distinct insulating states at v = 2, driven by vertical displacement field D and vertical magnetic field B. These insulating phases are distinguished as spin-antiferromagnetic, spin-polarized, and valley-polarized insulators, based on their responses to parallel and perpendicular magnetic fields. When electrons are polarized toward the moire superlattice, in a device with large twist angle, insulating states appear at v = 1/3 and 2/3 at zero magnetic field, and v = 1/2 in a magnetic field. Our findings reveal a rich interplay of charge, isospin, topology and magnetic field in rhombohedral graphene moire superlattices.

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Jian Zheng, Size Wu, Kai Liu, Bosai Lyu, Shuhan Liu, Yating Sha, Zhengxian Li, Kenji Watanabe, Takashi Taniguchi, Jinfeng Jia, Zhiwen Shi, Guorui Chen. 2024-12-13. Switchable Chern insulator, isospin competitions and charge density waves in rhombohedral graphene moire superlattices. https://arxiv.org/abs/2412.09985

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