Moiréless correlations in ABCA graphene

Proceedings of the National Academy of Sciences, vol. 118

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 moiré 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 16

1. Alexander Kerelsky

   Columbia University

   Affiliation as printed

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

2. Carmen Rubio-Verdú

   Columbia University

   Affiliation as printed

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

3. Lede Xian

   Songshan Lake Materials Laboratory · Max Planck Institute for the Structure and Dynamics of Matter

   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;

4. 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;

5. Dorri Halbertal

   Columbia University

   Affiliation as printed

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

6. Nathan Finney

   Columbia University

   Affiliation as printed

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

7. Larry Song

   Columbia University

   Affiliation as printed

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

8. Simon Turkel

   Columbia University

   Affiliation as printed

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

9. Lei Wang

   Columbia University

   Affiliation as printed

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

10. Kenji Watanabe

    National Institute for Materials Science

    Affiliation as printed

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

11. Takashi Taniguchi

    National Institute for Materials Science

    Affiliation as printed

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

12. James Hone

    Columbia University

    Affiliation as printed

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

13. Cory R. Dean

    Columbia University

    Affiliation as printed

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

14. D. N. Basov

    Columbia University

    Affiliation as printed

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

15. Ángel Rubio

    University of the Basque Country · Max Planck Institute for the Structure and Dynamics of Matter · Flatiron Institute

    Affiliation as printed

    Center for Computational Quantum Physics, The Flatiron Institute, New York, NY 10010;

    Nano-Bio Spectroscopy Group, Departamento de Fisica de Materiales, Universidad del País Vasco, 20018 San Sebastian, Spain

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

16. Abhay N. Pasupathy

    Columbia University

    Affiliation as printed

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