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Greif, Daniel

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Greif

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Greif, Daniel

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2017 - 20192

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Author's Publications: search.filters.isAuthorOfPublication.3c6e0af0-ffcc-4e05-8557-37bba8fb1f83

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    String Patterns in the Doped Hubbard Model
    (American Association for the Advancement of Science (AAAS), 2019-07-18) Ji, Geoffrey; Bohrdt, Annabelle; Xu, Muqing; Knap, Michael; Demler, Eugene; Greiner, Markus; Greif, Daniel; Chiu, Christie; Grusdt, Fabian
    Understanding strongly correlated quantum many-body states is one of the most difficult challenges in modern physics. For example, there remain fundamental open questions on the phase diagram of the Hubbard model, which describes strongly correlated electrons in solids. In this work, we realize the Hubbard Hamiltonian and search for specific patterns within the individual images of many realizations of strongly correlated ultracold fermions in an optical lattice. Upon doping a cold-atom antiferromagnet, we find consistency with geometric strings, entities that may explain the relationship between hole motion and spin order, in both pattern-based and conventional observables. Our results demonstrate the potential for pattern recognition to provide key insights into cold-atom quantum many-body systems.
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    A cold-atom Fermi–Hubbard antiferromagnet
    (Springer Nature, 2017) Mazurenko, Anton; Chiu, Christie; Parsons, Maxwell Fredrick; Kanasz-Nagy, Marton; Schmidt, Richard; Bohrdt Grusdt, Fabian; Demler, Eugene; Greif, Daniel; Greiner, Markus
    Exotic phenomena in strongly correlated electron systems emerge from the interplay between spin and motional degrees of freedom. For example, doping an antiferromagnet is expected to give rise to pseudogap states and high-temperature superconductors. Quantum simulation with ultracold fermions in optical lattices offers the potential to answer open questions about the doped Hubbard Hamiltonian, and has recently been advanced by quantum gas microscopy. Here we report the realization of an antiferromagnet in a repulsively interacting Fermi gas on a 2D square lattice of about 80 sites. The antiferromagnetic long-range order (LRO) manifests at our lowest temperatures of T/t = 0.25(2) through the divergence of the correlation length that reaches the size of the system, the development of a peak in the spin structure factor and a value of the staggered magnetization approaching the ground state value. We hole-dope the system away from half filling, where interesting states are expected, and find that strong magnetic correlations persist at the antiferromagnetic wavevector to dopings of about 15%. In this regime numerical simulations become very challenging and experiments can provide a valuable benchmark. Our results demonstrate that Fermi gas microscopy can address open questions on the low-temperature Hubbard model.