Observation of antiferromagnetic correlations in an ultracold SU( N ) Hubbard model

Mott insulators are paradigmatic examples of strongly correlated physics from which many phases of quantum matter with hard-to-explain properties emerge. Extending the typical SU(2) spin symmetry of Mott insulators to SU( N ) is predicted to produce exotic quantum magnetism at low temperatures. In this work, we experimentally observe nearest-neighbour spin correlations in a SU(6) Hubbard model realized by ytterbium atoms in optical lattices. We study one-dimensional, two-dimensional square and three-dimensional cubic lattice geometries. The measured SU(6) spin correlations are enhanced compared with the SU(2) correlations, owing to strong Pomeranchuk cooling. The experimental data for a one-dimensional lattice agree qualitatively with our theoretical calculations, with an error of at most 30%, without any fitting parameters. Detailed comparison between theory and experiment allows us to infer the temperature to be the lowest achieved for a cold-atom Fermi–Hubbard model. For three-dimensional lattices, the experiments reach entropies below the regime where our calculations converge, highlighting the importance of these experiments as quantum simulations.