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Journal Article

Moiréless correlations in ABCA graphene

MPS-Authors
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Xian,  L. D.
Theory Group, Theory Department, Max Planck Institute for the Structure and Dynamics of Matter, Max Planck Society;
Frontier Research Center, Songshan Lake Materials Laboratory;

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Kennes,  D. M.
Theory Group, Theory Department, Max Planck Institute for the Structure and Dynamics of Matter, Max Planck Society;
Institut für Theorie der Statistischen Physik, RWTH Aachen University, 2056 Aachen, Germany and JARA-Fundamentals of Future Information Technology;
Jülich Aachen Research Alliance-Fundamentals of Future Information Technology;

/persons/resource/persons22028

Rubio,  A.
Theory Group, Theory Department, Max Planck Institute for the Structure and Dynamics of Matter, Max Planck Society;
Center for Computational Quantum Physics (CCQ), The Flatiron Institute;
Nano-Bio Spectroscopy Group, Departamento de Fisica de Materiales, Universidad del Pas Vasco;

External Ressource
Fulltext (public)

e2017366118.full.pdf
(Publisher version), 2MB

Supplementary Material (public)

pnas.2017366118.sapp.pdf
(Supplementary material), 9MB

Citation

Kerelsky, A., Rubio-Verdú, C., Xian, L. D., Kennes, D. M., Halbertal, D., Finney, N., et al. (2021). Moiréless correlations in ABCA graphene. Proceedings of the National Academy of Sciences of the United States of America, 118(4): e2017366118. doi:10.1073/pnas.2017366118.


Cite as: http://hdl.handle.net/21.11116/0000-0005-43C1-5
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.