Spin-imbalance in a 2D Fermi-Hubbard system.

Brown, Peter T; Mitra, Debayan; Guardado-Sanchez, Elmer; Schauß, Peter; Kondov, Stanimir S; Khatami, Ehsan; Paiva, Thereza; Trivedi, Nandini et al. · Science · 2017

basic_science · Level V

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Abstract

The interplay of strong interactions and magnetic fields gives rise to unusual forms of superconductivity and magnetism in quantum many-body systems. Here, we present an experimental study of the two-dimensional Fermi-Hubbard model-a paradigm for strongly correlated fermions on a lattice-in the presence of a Zeeman field and varying doping. Using site-resolved measurements, we revealed anisotropic antiferromagnetic correlations, a precursor to long-range canted order. We observed nonmonotonic behavior of the local polarization with doping for strong interactions, which we attribute to the evolution from an antiferromagnetic insulator to a metallic phase. Our results pave the way to experimentally mapping the low-temperature phase diagram of the Fermi-Hubbard model as a function of both doping and spin polarization, for which many open questions remain.