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

• Published in: arXiv.org 2022-07
• Main Authors: Hagymási, Imre, Mohammad Syahid Mohd Isa, Tajkov, Zoltán, Márity, Krisztián, Oroszlány László, Koltai, János, Alassaf, Assem, Kun, Péter, Konrád Kandrai, Pálinkás, András, Vancsó, Péter, Tapasztó, Levente, Nemes-Incze, Péter
• Format: Article
• Language: English
• Subjects: Antiferromagnetism; Charge density; Complex compounds; Graphite; Ground state; High temperature; Magnetism; Magnets; Scanning tunneling microscopy; Spintronics; Superconductivity
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2201.10844

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.