Twisted Graphene Superlattices: Superconductivity, Electron Correlations and Beyond

Invited

Abstract

The understanding of strongly-correlated quantum matter has challenged physicists for decades. Such difficulties have stimulated new research paradigms, such as ultra-cold atom lattices for simulating quantum materials. In this talk I will present a new platform to investigate strongly correlated physics, based on graphene moiré superlattices. In particular, when two graphene sheets are twisted by an angle close to the theoretically predicted ‘magic angle’, the resulting flat band structure near the Dirac point gives rise to a strongly-correlated electronic system[1]. These flat bands exhibit half-filling insulating phases at zero magnetic field, which we show to be a Mott-like insulator arising from electrons localized in the moiré superlattice[2]. Moreover, upon doping, we find electrically tunable superconductivity in this system, with many characteristics similar to high-temperature cuprates superconductivity[3]. These unique properties of magic-angle twisted bilayer graphene open up a new playground for exotic many-body quantum phases in a 2D platform made of pure carbon and without magnetic field. Since these discoveries, a large number of theoretical models have been proposed based on the magic-angle graphene superlattices and beyond. I will also discuss our data demonstrating nematic superconductivity as well as correlated states in other types of graphene superlattices. The easy accessibility of the flat bands, the electrical tunability, and the bandwidth tunability though twist angle may pave the way towards more exotic correlated systems, such as quantum spin liquids.
[1] R. Bistritzer et. al., PNAS 108, 12233-12237 (2011).
[2] Y. Cao et al., Nature 556, 80-84 (2018)
[3] Y. Cao et al., Nature 556, 43-50 (2018)

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Presenters

  • Yuan Cao

    Department of Physics, Massachusetts Institute of Technology, Massachusetts Institute of Technology

Authors

  • Yuan Cao

    Department of Physics, Massachusetts Institute of Technology, Massachusetts Institute of Technology

  • Daniel Rodan Legrain

    Department of Physics, Massachusetts Institute of Technology, Massachusetts Institute of Technology, Physics, Massachusetts Institute of Technology, Dept. of Physics, Massachusetts Institute of Technology, USA

  • Oriol Rubies-Bigorda

    Department of Physics, Massachusetts Institute of Technology, Physics, Massachusetts Institute of Technology, Massachusetts Institute of Technology

  • Valla Fatemi

    Department of Physics, Massachusetts Institute of Technology, Massachusetts Institute of Technology, Yale Univ, Applied Physics, Yale University, Department of Applied Physics, Yale University

  • Shiang Fang

    Department of Physics, Harvard University, Physics, Harvard University, Harvard University

  • Kenji Watanabe

    National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305 0044, Japan, Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan, National Institute for Materials Science, Advanced Materials Laboratory, National Institute for Materials Science, , 1-1 Namiki, Tsukuba 305-0044, Japan, National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, National Institute of Materials Science, NIMS, Japan, Advanced Materials Laboratory, NIMS, National Institute for Materials Science, Tsukuba, Japan, National Institute for Materials Science, Japan, Advanced Materials Laboratory, National Institute for Materials Science, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0044, Japan, National Institute for Materials Science (NIMS), NIMS Tsukuba, National Institute for Materials Science (Japan), NIMS, National Institute for Material Science, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Japan, National Institute for Materials Science , Japan, National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan., Advanced Materials Laboratory, National Institute for Materials Science, Japan, Advanced Materials Laboratory, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan, National Institute for Materials Science, Tsukuba, Ibaraki 305- 0044, Japan, National Institute for Material Science - Japan, National Institute for Materials Science, Namiki Tsukuba Ibaraki, Japan, National Institute of Material Science, Advanced Material Lab, NIMS, Advanced Materials Laboratory, National Institute for Materials Science, Tsukuba, Japan, Advanced Materials Laboratory, National Institute for Materials Science, Tsukuba, Ibaraki, Japan, National Institute for Materials Science, Tsukuba, 1-1 Namiki, Tsukuba, National Institute for Materials Science, NIMS/Tsukuba, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044 Japan, National Institute for Materials Science, Namiki, 305-0044, Japan, National Institute for Material Science, Japan, Advanced Materials Laboratory, NIMS, Japan, Columbia University, Advanced Materials Labaratory, National Institute for Materials Science, National Institute of Material Science, 1-1 Namiki, Tsukuba, Ibaraki 205-0044, Japan, National Institute of Materials Science, Japan

  • Takashi Taniguchi

    National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305 0044, Japan, National Institute for Materials Science, Advanced Materials Laboratory, National Institute for Materials Science, , 1-1 Namiki, Tsukuba 305-0044, Japan, National Institute for Material Science, 1-1 Namiki, Tsukuba 305-0044, National Institute of Materials Science, NIMS, Japan, Advanced Materials Laboratory, NIMS, National Institute for Materials Science, Tsukuba, Japan, Advanced Materials Laboratory, National Institute for Materials Science, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0044, Japan, National Institute for Materials Science (NIMS), NIMS Tsukuba, NIMS, National Institute for Material Science, National Institute for Materials Science, Japan, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Japan, National Institute for Materials Science , Japan, Advanced Materials Laboratory, National Institute for Materials Science, Japan, Advanced Materials Laboratory, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan, National Institute for Materials Science, Tsukuba, Ibaraki 305- 0044, Japan, National Institute for Material Science - Japan, National Institute for Materials Science, Namiki Tsukuba Ibaraki, Japan, National Institute of Material Science, Advanced Material Lab, NIMS, Advanced Materials Laboratory, National Institute for Materials Science, Tsukuba, Japan, Advanced Materials Laboratory, National Institute for Materials Science, Tsukuba, Ibaraki, Japan, National Institute for Materials Science, Tsukuba, 1-1 Namiki, Tsukuba, National Institute for Materials Science, NIMS/Tsukuba, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044 Japan, National Institute for Materials Science, Namiki, 305-0044, Japan, National Institute for Material Science, Japan, Advanced Materials Laboratory, NIMS, Japan, Advanced Materials Labaratory, National Institute for Materials Science, National Institute of Material Science, 1-1 Namiki, Tsukuba, Ibaraki 205-0044, Japan, National Institute of Materials Science, Japan

  • Efthimios Kaxiras

    Harvard University, Department of Physics, Harvard University, Physics, Harvard University

  • Pablo Jarillo-Herrero

    Physics, Massachusetts Institute of Technology, Department of Physics, Massachusetts Institute of Technology, Massachusetts Institute of Technology, Dept. of Physics, Massachusetts Institute of Technology, USA, Massachusetts Inst of Tech-MIT, Physics, MIT