Observation of flat band in twisted double bilayer graphene using nanoARPES

ORAL

Abstract

The strong correlation physics leads to observing superconductivity and insulating states in twisted bilayer graphene at the magic angle [1,2]. Similarly, twisted double bilayer graphene (tDBG) has been predicted to host remarkably flat bands at narrow regions around the magic angle (θ ~ 1.3 ˚) [3]. A direct method to understand this correlated electron physics is the evolution of band topology by tuning the density of states. We use in-operando angle-resolved photoemission spectroscopy with nanometer scale (nanoARPES) spatial resolution to study the tDBG device with the twist angle ~2.6 ± 0.2˚. A remarkable change in the band topology can be observed with the tuning of the charge carrier density using back gate voltages. Moiré miniband with flat dispersions over the whole mini-Brillouin zone is observed at higher gate voltage (Vg ≥ 6V). This flat band is separated from the dispersive Dirac bands, leading to multiple moiré hybridization. The application of external electric fields provides a control mechanism over the bandwidth and flat-band structure and unveils the electron−electron interaction phenomena at different filling factors with in situ electrostatic gating.

[1] Cao, Y. et al. Nature 556, 80–84 (2018).

[2] Cao, Y. et al. Nature 556, 43–50 (2018).

[3] Shen, C., Chu, Y., Wu, Q. et al. Nat. Phys. 16, 520–525 (2020).

* This project is supported by the U.S. Department office of science, of the U.S. Department of Energy under Award No. DE-SC0020323

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Presenters

  • SOUVIK SASMAL

    Carnegie Mellon University

Authors

  • SOUVIK SASMAL

    Carnegie Mellon University

  • Alfred J Jones

    Department of Physics and Astronomy, Aarhus University, Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark

  • Ryan Muzzio

    Carnegie Mellon University

  • Paulina Ewa Majchrzak

    Department of Physics and Astronomy, Aarhus University

  • 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, National Institute for Material Science

  • 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

  • Simranjeet Singh

    Carnegie Mellon Univ.

  • Christopher Jozwiak

    Lawrence Berkeley National Lab, Lawrence Berkeley National Laboratory, Berkeley National Lab, Advanced Light Source, The Advanced Light Source, Lawrence Berkeley National Laboratory, Advanced Light Source, Lawrence Berkeley National Laboratory

  • Aaron Bostwick

    Lawrence Berkeley National Lab, Lawrence Berkeley National Laboratory, Berkeley National Lab, Advanced Light Source, The Advanced Light Source, Lawrence Berkeley National Laboratory, Advanced Light Source, Lawrence Berkeley National Laboratory

  • Eli Rotenberg

    Lawrence Berkeley National Laboratory

  • Søren Ulstrup

    Department of Physics and Astronomy, Aarhus University, Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark

  • Jyoti Katoch

    Carnegie Mellon University