Moireless Correlations in ABCA Graphene

Hispana

Abstract

Atomically thin van der Waals materials stacked with an interlayer twist have proven to be an excellent platform toward achieving gate-tunable correlated phenomena linked to the formation of flat electronic bands. In this work we demonstrate the formation of emergent correlated phases in multilayer rhombohedral graphene-a simple material that also exhibits a flat electronic band edge but without the need of having a moire superlattice induced by twisted van der Waals layers. We show that two layers of bilayer graphene that are twisted by an arbitrary tiny angle host large (micrometer-scale) regions of uniform rhombohedral four-layer (ABCA) graphene that can be independently studied. Scanning tunneling spectroscopy reveals that ABCA graphene hosts an unprecedentedly sharp van Hove singularity of 3-5-meV half-width. We demonstrate that when this van Hove singularity straddles the Fermi level, a correlated many-body gap emerges with peak-to-peak value of 9.5 meV at charge neutrality. Mean-field theoretical calculations for model with short-ranged interactions indicate that two primary candidates for the appearance of this broken symmetry state are a charge-transfer excitonic insulator and a ferrimagnet. Finally, we show that ABCA graphene hosts surface topological helical edge states at natural interfaces with ABAB graphene which can be turned on and off with gate voltage, implying that small-angle twisted double-bilayer graphene is an ideal programmable topological quantum material

Authors 14

1. Alexander Kerelsky

   Columbia University

   Affiliation as printed

   Department of Physics, Columbia University, New York, NY 10027;

2. Lede Xian

   Songshan Lake Materials Laboratory · Max Planck Institute for the Structure and Dynamics of Matter · University of California, Berkeley

   Affiliation as printed

   Frontier Research Center, Songshan Lake Materials Laboratory, 523808 Dongguan, Guangdong, China;

   Theory Department, Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany;

   University of California, Berkeley; M

3. Dante Marvin Kennes Aachen Institut für Theorie der Statistischen Physik

   Jülich Aachen Research Alliance · Max Planck Institute for the Structure and Dynamics of Matter · RWTH Aachen University

   Affiliation as printed

   Institut für Theorie der Statistischen Physik, Rheinisch-Westfälische Technische Hochschule Aachen University, 52056 Aachen, Germany;

   Jülich Aachen Research Alliance-Fundamentals of Future Information Technology, 52056 Aachen, Germany;

   Theory Department, Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany;

4. Dorri Halbertal

   Columbia University

   Affiliation as printed

   Department of Physics, Columbia University, New York, NY 10027;

5. Nathan Finney

   Columbia University

   Affiliation as printed

   Department of Mechanical Engineering, Columbia University, New York, NY 10027;

6. Larry Song

   Columbia University

   Affiliation as printed

   Department of Physics, Columbia University, New York, NY 10027;

7. Simon Turkel

   Columbia University

   Affiliation as printed

   Department of Physics, Columbia University, New York, NY 10027;

8. Lei Wang

   Columbia University

   Affiliation as printed

   Department of Physics, Columbia University, New York, NY 10027;

9. Kenji Watanabe

   National Institute for Materials Science · University of California, Berkeley

   Affiliation as printed

   National Institute for Materials Science, 1-1 Namiki, 305-0044 Tsukuba, Japan;

   University of California, Berkeley; M

10. Takashi Taniguchi

    National Institute for Materials Science · University of California, Berkeley

    Affiliation as printed

    National Institute for Materials Science, 1-1 Namiki, 305-0044 Tsukuba, Japan;

    University of California, Berkeley; M

11. James Hone

    Columbia University

    Affiliation as printed

    Department of Mechanical Engineering, Columbia University, New York, NY 10027;

12. Cory R. Dean

    Columbia University

    Affiliation as printed

    Department of Physics, Columbia University, New York, NY 10027;

13. D. N. Basov

    Columbia University

    Affiliation as printed

    Department of Physics, Columbia University, New York, NY 10027;

14. Abhay N. Pasupathy

    Columbia University

    Affiliation as printed

    Department of Physics, Columbia University, New York, NY 10027;