Browsing by Author "Huse, David A."

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    Enlarging and cooling the N´eel state in an optical lattice
    (American Physical Society, 2012) Mathy, Charles J.M.; Huse, David A.; Hulet, Randall G.
    We propose an experimental scheme to favor both the realization and the detection of the N´eel state in a two-component gas of ultracold fermions in a three-dimensional simple-cubic optical lattice. By adding three compensating Gaussian laser beams to the standard three pairs of retroreflected lattice beams, and adjusting the relative waists and intensities of the beams, one can significantly enhance the size of the N´eel state in the trap, thus increasing the signal of optical Bragg scattering. Furthermore, the additional beams provide for adjustment of the local chemical potential and the possibility to evaporatively cool the gas while in the lattice. Our proposals are also relevant to efforts to realize other many-body quantum phases in optical lattices.
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    Observation of antiferromagnetic correlations in the Hubbard model with ultracold atoms
    (Nature Publishing Group, 2015) Hart, Russell A.; Duarte, Pedro M.; Yang, Tsung-Lin; Liu, Xinxing; Paiva, Thereza; Khatami, Ehsan; Scalettar, Richard T.; Trivedi, Nandini; Huse, David A.; Hulet, Randall G.; Rice Quantum Institute
    Ultracold atoms in optical lattices have great potential to contribute to a better understanding of some of the most important issues in many-body physics, such as high-temperature superconductivity[1]. The Hubbard model—a simplified representation of fermions moving on a periodic lattice—is thought to describe the essential details of copper oxide superconductivity[2]. This model describes many of the features shared by the copper oxides, including an interaction-driven Mott insulating state and an antiferromagnetic (AFM) state. Optical lattices filled with a two-spin-component Fermi gas of ultracold atoms can faithfully realize the Hubbard model with readily tunable parameters, and thus provide a platform for the systematic exploration of its phase diagram[3, 4]. Realization of strongly correlated phases, however, has been hindered by the need to cool the atoms to temperatures as low as the magnetic exchange energy, and also by the lack of reliable thermometry[5]. Here we demonstrate spin-sensitive Bragg scattering of light to measure AFM spin correlations in a realization of the three-dimensional Hubbard model at temperatures down to 1.4 times that of the AFM phase transition. This temperature regime is beyond the range of validity of a simple high-temperature series expansion, which brings our experiment close to the limit of the capabilities of current numerical techniques, particularly at metallic densities. We reach these low temperatures using a compensated optical lattice technique[6], in which the confinement of each lattice beam is compensated by a blue-detuned laser beam. The temperature of the atoms in the lattice is deduced by comparing the light scattering to determinant quantum Monte Carlo simulations[7] and numerical linked-cluster expansion[8] calculations. Further refinement of the compensated lattice may produce even lower temperatures which, along with light scattering thermometry, would open avenues for producing and characterizing other novel quantum states of matter, such as the pseudogap regime and correlated metallic states of the two-dimensional Hubbard model.