Coulomb interactions and migrating Dirac cones imaged by local quantum oscillations in twisted graphene

Matan Bocarsly; Indranil Roy; Vishal Bhardwaj; Matan Uzan; Patrick Ledwith; Gal Shavit; Nasrin Banu; Yaozhang Zhou; Yuri Myasoedov; Kenji Watanabe; Takashi Taniguchi; Yuval Oreg; Daniel E. Parker; Yuval Ronen; Eli Zeldov

doi:10.1038/s41567-025-02786-z

Coulomb interactions and migrating Dirac cones imaged by local quantum oscillations in twisted graphene

Matan Bocarsly, Indranil Roy, Vishal Bhardwaj, Matan Uzan, Patrick Ledwith, Gal Shavit, Nasrin Banu, Yaozhang Zhou, Yuri Myasoedov, Kenji Watanabe, Takashi Taniguchi, Yuval Oreg, Daniel E. Parker, Yuval Ronen, Eli Zeldov

Department of Condensed Matter Physics

Research output: Contribution to journal › Article › peer-review

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Abstract

Flat-band moiré graphene systems are a quintessential platform for investigating correlated phases of matter. Various interaction-driven ground states have been proposed, but despite extensive experimental effort, there has been little direct evidence that distinguishes between various phases, in particular near the charge neutrality point. Here we probe the fine details of the density of states and the effects of Coulomb interactions in alternating-twist trilayer graphene by imaging the local thermodynamic quantum oscillations with a nanoscale scanning superconducting quantum interference device. We find that the charging self-energy due to occupied electronic states is most important in explaining the high-carrier-density physics. At half-filling of the conduction flat band, we observe ferromagnetic-driven symmetry breaking, suggesting that it is the most robust mechanism in the hierarchy of phase transitions. Near charge neutrality, where exchange energy dominates over charging self-energy, we find a nematic semimetal ground state, which is theoretically favoured over gapped states in the presence of heterostrain. In this semimetallic phase, the flat-band Dirac cones migrate towards the mini-Brillouin zone centre, spontaneously breaking the threefold rotational symmetry. Our low-field local quantum oscillation technique can be used to explore the ground states of many strongly interacting van der Waals systems.

Original language	English
Pages (from-to)	421-429
Number of pages	17
Journal	Nature Physics
Volume	21
Issue number	3
Early online date	14 Feb 2025
DOIs	https://doi.org/10.1038/s41567-025-02786-z
Publication status	Published - Mar 2025

Funding

We thank P. Emanuel for fruitful discussions. This work was co-funded by the Minerva Foundation (Grant No. 140687), the United States–Israel Binational Science Foundation (Grant No. 2022013) and by the European Union (MoireMultiProbe, Grant No. 101089714). The views and opinions expressed are, however, those of the authors only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them. E.Z. acknowledges the support of the Andre Deloro Prize for Scientific Research, Goldfield Family Charitable Trust, and the Leona M. and Harry B. Helmsley Charitable Trust (Grant No. 2112-04911). Y.R. acknowledges funding received from the MINERVA Stiftung with funds from the BMBF of the Federal Republic of Germany. K.W. and T.T. acknowledge support from the JSPS KAKENHI (Grant Nos. 20H00354, 21H05233 and 23H02052) and the World Premier International Research Center Initiative, MEXT, Japan. G.S. acknowledges support from the Walter Burke Institute for Theoretical Physics at Caltech and from the Yad Hanadiv Foundation through the Rothschild fellowship. Y.O. acknowledges support from the European Union’s Horizon 2020 research and innovation programme (Grant Agreement LEGOTOP No. 788715), and the DFG (CRC/Transregio 183, EI 519/7-1). D.E.P. is supported by the Simons Collaboration on UltraQuantum Matter as a grant from the Simons Foundation and by start-up funding from the University of California at San Diego. M.B. acknowledges the VATAT Outstanding PhD Fellowship in Quantum Science and Technology.

All Science Journal Classification (ASJC) codes

General Physics and Astronomy

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ez_NatPhysics_CoulombInteractionsandMigrating_PV2025Final published version, 7.35 MBLicence: CC BY

Cite this

Bocarsly, M., Roy, I., Bhardwaj, V., Uzan, M., Ledwith, P., Shavit, G., Banu, N., Zhou, Y., Myasoedov, Y., Watanabe, K., Taniguchi, T., Oreg, Y., Parker, D. E., Ronen, Y., & Zeldov, E. (2025). Coulomb interactions and migrating Dirac cones imaged by local quantum oscillations in twisted graphene. Nature Physics, 21(3), 421-429. https://doi.org/10.1038/s41567-025-02786-z

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abstract = "Flat-band moir{\'e} graphene systems are a quintessential platform for investigating correlated phases of matter. Various interaction-driven ground states have been proposed, but despite extensive experimental effort, there has been little direct evidence that distinguishes between various phases, in particular near the charge neutrality point. Here we probe the fine details of the density of states and the effects of Coulomb interactions in alternating-twist trilayer graphene by imaging the local thermodynamic quantum oscillations with a nanoscale scanning superconducting quantum interference device. We find that the charging self-energy due to occupied electronic states is most important in explaining the high-carrier-density physics. At half-filling of the conduction flat band, we observe ferromagnetic-driven symmetry breaking, suggesting that it is the most robust mechanism in the hierarchy of phase transitions. Near charge neutrality, where exchange energy dominates over charging self-energy, we find a nematic semimetal ground state, which is theoretically favoured over gapped states in the presence of heterostrain. In this semimetallic phase, the flat-band Dirac cones migrate towards the mini-Brillouin zone centre, spontaneously breaking the threefold rotational symmetry. Our low-field local quantum oscillation technique can be used to explore the ground states of many strongly interacting van der Waals systems.",

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AU - Ledwith, Patrick

AU - Shavit, Gal

AU - Banu, Nasrin

AU - Zhou, Yaozhang

AU - Myasoedov, Yuri

AU - Watanabe, Kenji

AU - Taniguchi, Takashi

AU - Oreg, Yuval

AU - Parker, Daniel E.

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AU - Zeldov, Eli

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Coulomb interactions and migrating Dirac cones imaged by local quantum oscillations in twisted graphene

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