Probing the Hofstadter's butterfly in graphene/hexagonal-boron nitride moire superlattice using infrared magneto-spectroscopy
ORAL
Abstract
Graphene on hexagonal boron nitride (hBN) exhibits a rotation-dependent moiré pattern. Perfect alignment causes the superlattice potential to match the magnetic length scale in graphene, yielding a butterfly-like energy spectrum. Infrared optical probes of cyclotron resonance can directly measure the associated energies by probing transitions across the fractal energy levels. We have fabricated high-quality monolayer graphene encapsulated with hBN, where the graphene layer forms a small twist angle of 0.5° with either the top or bottom hBN flake. The on-site energy difference results in the splitting of the valley-polarized zeroth Landau level creating a valley gap, where the periodicity of the moiré superlattice can modulate the gap size. For a rotational alignment of 0.5°, we measured the valley gap of approximately 12 meV using magneto-infrared spectroscopy. Additionally, we observed unusual broadening and splitting in the Landau level transitions at magnetic field below 6T, beyond what is typically observed in monolayer graphene. These phenomena are likely to arise from the fractal spectrum.
*NSF CAREER DMR – 1945278
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Presenters
Yashika Kapoor
Washington University, St. Louis
Authors
Yashika Kapoor
Washington University, St. Louis
Xinyi Du
Washington University, St. Louis
Washington University in St. Louis
Gwyneth Phillips
Washington University in Saint Louis
Takashi Taniguchi
Kyoto Univ
National Institute for Materials Science
Research Center for Materials Nanoarchitectonics
Research Center for Materials Nanoarchitectonics, National Institute for Materials Science
National Institute for Materials Sciences
NIMS
International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
National Institute for Material Science
International Center for Materials Nanoarchitectonics, NIMS, Japan
International Center for Materials Nanoarchitectonics, Tsukuba
National Institue for Materials Science
Kyoto University
National Institute of Materials Science
International Center for Materials Nanoarchitectonics and National Institute for Materials Science
Kenji Watanabe
National Institute for Materials Science
NIMS
Research Center for Electronic and Optical Materials, National Institute for Materials Science
Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
