Hubbard model

Ultracold atom

Physics

Mott insulator

Antiferromagnetism

Quantum simulator

Magnetism

Acoustics

Superfluidity

Condensed matter physics

Square lattice

Lattice (music)

Spin (aerodynamics)

Ising model

Fermion

Superconductivity

Quantum computer

Quantum mechanics

Quantum phase transition

Quantum phases

Quantum

Optical lattice

Thermodynamics

Nature Physics

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. A cold-atom simulator has realized a popular many-body model of quantum magnetism in regimes that cannot be easily studied theoretically, achieving the record-coldest fermions ever seen.

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