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arXiv · 2201.10844

Observation of competing, correlated ground states in the flat band of rhombohedral graphite

Imre Hagymási·Mohammad Syahid Mohd Isa·Zoltán Tajkov·Krisztián Márity·Oroszlány László·János Koltai·Assem Alassaf·Péter Kun·Konrád Kandrai·András Pálinkás·Péter Vancsó·Levente Tapasztó·Péter Nemes-Incze
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Abstract

In crystalline solids the interactions of charge and spin can result in a variety of emergent quantum ground states, especially in partially filled, topological flat bands such as Landau levels or in 'magic-angle' bilayer graphene. Much less explored is rhombohedral graphite (RG), perhaps the simplest and structurally most perfect condensed matter system to host a flat band protected by symmetry. By scanning tunneling microscopy we map the flat band charge density of 8, 10 and 17 layers and identify a domain structure emerging from a competition between a sublattice antiferromagnetic insulator and a gapless correlated paramagnet. Our density-matrix renormalization group calculations explain the observed features and demonstrate that the correlations are fundamentally different from graphene based magnetism identified until now, forming the ground state of a quantum magnet. Our work establishes RG as a new platform to study many-body interactions beyond the mean-field approach, where quantum fluctuations and entanglement dominate.

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Imre Hagymási, Mohammad Syahid Mohd Isa, Zoltán Tajkov, Krisztián Márity, Oroszlány László, János Koltai, Assem Alassaf, Péter Kun, Konrád Kandrai, András Pálinkás, Péter Vancsó, Levente Tapasztó, Péter Nemes-Incze. 2022-01-26. Observation of competing, correlated ground states in the flat band of rhombohedral graphite. https://doi.org/10.1126/sciadv.abo6879

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