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Frustration and Kinetic Magnetism in a Fermi-Hubbard Quantum Simulator

ORAL

Abstract

We report on recent experimental quantum simulations of strongly correlated materials with ultracold fermions, revealing emergent magnetic states in a Hubbard model with tunable geometric frustration and doping. Using an optical lattice that transitions from a square to a triangular geometry, we observe the transformation of a Néel antiferromagnet into a short-range 120° spiral state at half-filling due to frustration. Beyond half-filling, antiferromagnetic correlations strengthen with hole dopants but intriguingly reverse to ferromagnetic with particle dopants. By measuring three-point dopant-spin-spin correlations, we uncover the emergence of ferromagnetic polarons, offering the first cold-atom observation of Nagaoka ferromagnetism. Our work provides insights into kinetic magnetism, akin to observations in twisted TMD bilayers, and opens new avenues for exploring dopant pairing mediated by frustration.

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Publication: M. Lebrat, M. Xu, et al, Observation of Nagaoka Polarons in a Fermi-Hubbard Quantum Simulator, arXiv:2308.12269<br>M. Xu, et al, Frustration- and doping-induced magnetism in a Fermi-Hubbard simulator, Nature 620, 971-976 (2023)

Presenters

  • Martin Lebrat

    Harvard University

Authors

  • Martin Lebrat

    Harvard University

  • Muqing Xu

    Harvard University

  • Lev H Kendrick

    Harvard University

  • Anant Kale

    Harvard University

  • Youqi Gang

    Harvard University

  • Geoffrey Ji

    Harvard University

  • Richard T Scalettar

    University of California, Davis

  • Pranav Seetharaman

    San Jose State University

  • Ivan Morera

    Universitat de Barcelona, University of Barcelona

  • Ehsan Khatami

    San Jose State University

  • Eugene Demler

    ETH Zurich

  • Markus Greiner

    Harvard University