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Author(s): M. Eric Tai [1]; Alexander Lukin [1]; Matthew Rispoli [1]; Robert Schittko [1]; Tim Menke [1]; Dan Borgnia [1]; Philipp M. Preiss [1]; Fabian Grusdt [1]; Adam M. Kaufman [...]

Author(s): Anton Mazurenko [1]; Christie S. Chiu [1]; Geoffrey Ji [1]; Maxwell F. Parsons [1]; Mrton Kansz-Nagy [1]; Richard Schmidt [1]; Fabian Grusdt [1]; Eugene Demler [1]; Daniel Greif [1]; [...]

Polarons--electronic charge carriers 'dressed' by a local polarization of the background environment--are among the most fundamental quasiparticles in interacting many-body systems, and emerge even at the level of a single dopant.sup.1. In the context of the two-dimensional Fermi-Hubbard model, polarons are predicted to form around charged dopants in an antiferromagnetic background in the low-doping regime, close to the Mott insulating state.sup.2-7; this prediction is supported by macroscopic transport and spectroscopy measurements in materials related to high-temperature superconductivity.sup.8. Nonetheless, a direct experimental observation of the internal structure of magnetic polarons is lacking. Here we report the microscopic real-space characterization of magnetic polarons in a doped Fermi-Hubbard system, enabled by the single-site spin and density resolution of our ultracold-atom quantum simulator. We reveal the dressing of doublons by a local reduction--and even sign reversal--of magnetic correlations, which originates from the competition between kinetic and magnetic energy in the system. The experimentally observed polaron signatures are found to be consistent with an effective string model at finite temperature.sup.7. We demonstrate that delocalization of the doublon is a necessary condition for polaron formation, by comparing this setting with a scenario in which a doublon is pinned to a lattice site. Our work could facilitate the study of interactions between polarons, which may lead to collective behaviour, such as stripe formation, as well as the microscopic exploration of the fate of polarons in the pseudogap and 'bad metal' phases. Magnetic polarons are imaged with single-site spin and density resolution in the low-doping regime of the atomic Fermi-Hubbard model, showing that mobile delocalized doublons are necessary for polaron formation., Author(s): Joannis Koepsell [sup.1] , Jayadev Vijayan [sup.1] , Pimonpan Sompet [sup.1] , Fabian Grusdt [sup.2] [sup.3] , Timon A. Hilker [sup.1] [sup.5] , Eugene Demler [sup.2] , Guillaume Salomon [...]

The interplay between magnetic fields and interacting particles can lead to exotic phases of matter that exhibit topological order and high degrees of spatial entanglement. Although these phases were discovered in a solid-state setting, recent innovations in systems of ultracold neutral atoms-uncharged atoms that do not naturally experience a Lorentz force-allow the synthesis of artificial magnetic, or gauge, fields. This experimental platform holds promise for exploring exotic physics in fractional quantum Hall systems, owing to the microscopic control and precision that is achievable in cold-atom systems. However, so far these experiments have mostly explored the regime of weak interactions, which precludes access to correlated many-body states. Here, through microscopic atomic control and detection, we demonstrate the controlled incorporation of strong interactions into a two-body system with a chiral band structure. We observe and explain the way in which interparticle interactions induce chirality in the propagation dynamics of particles in a ladder-like, real-space lattice governed by the interacting Harper-Hofstadter model, which describes lattice-confined, coherently mobile particles in the presence of a magnetic field. We use a bottom-up strategy to prepare interacting chiral quantum states, thus circumventing the challenges of a top-down approach that begins with a many-body system, the size of which can hinder the preparation of controlled states. Our experimental platform combines all of the necessary components for investigating highly entangled topological states, and our observations provide a benchmark for future experiments in the fractional quantum Hall regime. [ABSTRACT FROM AUTHOR]