High-order minibands and interband Landau level reconstruction in graphene moiré superlattices

Xiaobo Lu, Jian Tang, John R. Wallbank, Shuopei Wang, Cheng Shen, Shuang Wu, Peng Chen, Wei Yang, Jing Zhang, Kenji Watanabe, Takashi Taniguchi, Rong Yang, Dongxia Shi, Dmitri K. Efetov, Vladimir I. Fal'ko, Guangyu Zhang

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    The propagation of Dirac fermions in graphene through a long-period periodic potential would result in a band folding together with the emergence of a series of cloned Dirac points (DPs) [C.-H. Park et al., Nat. Phys. 4, 213 (2008); C.-H. Park et al.Phys. Rev. Lett. 101, 126804 (2008)]. In highly aligned graphene/hexagonal boron nitride (G/hBN) heterostructures, the lattice mismatch between the two atomic crystals generates a unique kind of periodic structure known as a moiré superlattice. Of particular interest is the emergent phenomena related to the reconstructed band-structure of graphene, such as the Hofstadter butterfly [L. A. Ponomarenko et al., Nature (London) 497, 594 (2013); B. Hunt et al., Science 340, 1427 (2013); C. R. Dean et al., Nature(London) 497, 598 (2013)], topological currents [R. V Gorbachev et al., Science 346, 448 (2014)], gate-dependent pseudospin mixing [Z. Shi et al., Nat. Phys. 10, 743 (2014)], and ballistic miniband conduction [M. Lee et al., Science 353, 1526 (2016)]. However, most studies so far have been limited to the lower-order minibands, e.g., the first and second minibands counted from charge neutrality, and consequently the fundamental nature of the reconstructed higher-order miniband spectra still remains largely unknown. Here we report on probing the higher-order minibands of precisely aligned graphene moiré superlattices by transport spectroscopy. Using dual electrostatic gating, the edges of these high-order minibands, i.e., the third and fourth minibands, can be reached. Interestingly, we have observed interband Landau level (LL) crossing inducing gap closures in a multiband magnetotransport regime, which originates from band overlap between the second and third minibands. As observed, high-order minibands and LL reconstruction qualitatively match our simulated results.
    Original languageEnglish
    JournalPhysical Review B
    Issue number4
    Early online date8 Jul 2020
    Publication statusPublished - 2020

    Research Beacons, Institutes and Platforms

    • National Graphene Institute


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