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Atomic-scale structure and electronic properties of twisted double bilayer graphene

ORAL

Abstract

The fundamental properties of 2D materials are dramatically modified when they are brought next to each other to form a vertical heterostructure. The electronic characteristics of such van der Waals materials can be further controlled by the twist angle degree of freedom, inducing electronic flat bands that lead to emergent phases such as correlated insulating (CI) and superconducting (SC) states in twisted bilayer graphene. Such phenomenology is expected in higher order heterostructures where the vertical stacking order plays a major role. Recent works showed that double bilayer graphene (tDBG) at a twist angle of ~1.3° hosts displacement field tunable CI and SC states, as well as ferromagnetic order. We show real-space imaging of tDBG moiré superstructure by means of Scanning Tunneling Microscopy/Spectroscopy (STM/STS). STS reveals the presence of van Hove singularities whose spatial distribution within the moiré unit cell is determined by the inequivalent stacking sites. Tuning carrier density and displacement field reveals long-range broken symmetries that emerge when the Fermi level is brought in the vicinity of such flat bands. Our results shed light into the underlying mechanisms behind electron-electron correlations in tDBG and the emergent ferromagnetic order.

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Presenters

  • Carmen Rubio Verdu

    Physics Department, Columbia University, Department of Physics, Columbia University, New York, New York 10027, USA, Physics, Columbia University

Authors

  • Carmen Rubio Verdu

    Physics Department, Columbia University, Department of Physics, Columbia University, New York, New York 10027, USA, Physics, Columbia University

  • Simon Eli Turkel

    Physics Department, Columbia University, Department of Physics, Columbia University, New York, New York 10027, USA

  • Larry Song

    Physics Department, Columbia University, Department of Physics, Columbia University, New York, New York 10027, USA

  • Dante Kennes

    Dahlem Center for Complex Quantum Systems and Fachbereich Physik, Freie Universität Berlin, Dahlem Center for Complex Quantum Systems and Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany, RWTH Aachen University, Institut fur Mathematische Physik, Technische Universitat Braunschweig, Institut für Theorie der Statistischen Physik, RWTH Aachen University

  • Lede Xian

    Max Planck Institute for the Structure and Dynamics of Matter

  • Hector Ochoa

    Physics Department, Columbia University, Columbia University, Department of Physics, Columbia University, New York, New York 10027, USA

  • Angel Rubio

    Theory Department, Max Planck Institute for the Structure and Dynamics of Matter, Center for Computational Quantum Physics (CCQ), The Flatiron Institute, Max Planck Institute for Structure and Dynamics of Matter, Department of Physics, Columbia University, New York, New York 10027, USA, Max Planck Institute for the Structure and Dynamics of Matter, Hamburg, Germany, Max Planck Institute for the Structure and Dynamics of Matter, Structure and Dynamics of Matter, Max Planck Institute, Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg, Germany, Max Planck Inst Structure & Dynamics of Matter, Max Planck Institue for the Structure and Dynamics of Matter, Theory, Max Planck Institute for the Structure & Dynamics of Matter

  • Abhay Pasupathy

    Columbia University, Physics Department, Columbia University, Columbia Univ, Department of Physics, Columbia University, New York, New York 10027, USA, Physics, Columbia University, Department of Physics, Columbia University