The article reports the direct observation of itinerant spin polarons in a triangular-lattice Hubbard system realized with ultracold atoms. Spin polarons are quasiparticles that arise from the interplay between the kinetic energy of doped charge carriers and spin interactions in strongly correlated materials.
In kinetically frustrated lattices, itinerant spin polarons are theoretically predicted to exist even without superexchange coupling. However, a microscopic observation of these polarons has been lacking. The authors use their ultracold atom system to directly image the local magnetic correlations around hole and charge dopants.
Around hole dopants, they observe enhanced antiferromagnetic correlations, a signature of itinerant spin polarons. In contrast, around charge dopants, they find ferromagnetic correlations, a manifestation of the elusive Nagaoka effect. The authors study the evolution of these correlations with interactions and doping, and use higher-order correlation functions to elucidate the relative contributions of superexchange and kinetic mechanisms.
The robustness of itinerant spin polarons at high temperature suggests potential mechanisms for hole pairing and superconductivity in frustrated systems. Furthermore, the work provides microscopic insights into related phenomena in triangular-lattice moiré materials.
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by Max L. Prich... à www.nature.com 05-08-2024
https://www.nature.com/articles/s41586-024-07356-6Questions plus approfondies