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In graphene moiré superlattices, while various gapped phases like correlated/(fractional) Chern insulators can be ascribed to spontaneous symmetry breaking, isospin Pomeranchuk effect in the gapless phase points out the coexistence of localized magnetic moment and itinerate electrons, consistent with the recent topological heavy fermion model based on which a Kondo lattice may fundamentally change the understanding of twisted bilayer graphene. However, so far the Pomeranchuk effect has only been observed at v=+/-1 (one electron/hole per cell), leaving open questions such as why or whether the effect is unique to this filling factor. Here by studying a rhombohedral trilayer graphene superlattice, we report that at v=-3 the gapless Fermi liquid changes to a correlated peak at elevated temperatures or in parallel magnetic fields. The Pomeranchuk effect also emerges at v=-1 and -2 in specific ranges of displacement fields. Furthermore, the Fermi-liquid ground state is also found to exhibit superconducting-like critical behaviors, probably resulting from out-of-equilibrium electron transport on an extremely flat Fermi sheet. Our results greatly expand the scope for observing the Pomeranchuk effect, i.e., around the phase boundary where the Stoner criteria is marginally satisfied and the flavor polarization order strongly fluctuates, shedding light on a universal physical model of flat

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• Creative Commons BY-NC-ND Attribution-NonCommercial-NoDerivs 4.0 International
  

Keyword: Isospin flavor polarization, rhombohedral trilayer graphene, symmetry-breaking phases

Date published: 2024-11-11

Publisher: Springer Science and Business Media LLC

Journal:

• Nature Communications (ISSN: 20411723) vol. 15 issue. 1 9765

Funding:

• National Natural Science Foundation of China 11974027
• Natural Science Foundation of Beijing Municipality 4222084

Manuscript type: Publisher's version (Version of record)

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First published URL: https://doi.org/10.1038/s41467-024-54200-6

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Updated at: 2025-02-06 12:30:53 +0900

Published on MDR: 2025-02-06 12:30:53 +0900