Browsing by Author "Paprotta, Tobias"

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    A 2D optical lattice for creating a 1-dimensional Fermi gas
    (2009) Paprotta, Tobias; Hulet, Randall G.
    Ultracold atomic gases can be prepared in laboratory environments with unrivaled control and purity. In one and a half decades the field has evolved from the first Bose condensates in dilute alkali gases to multiple species mixtures and degenerate Fermi systems. Combining quantum degenerate fermions and optical lattices enables the simulation of relevant condensed matter systems. By observing the final state of an atomic sample in a tailored optical potential the system can be used as an analog quantum computer to evaluate Hamiltonians that are computationally impossible to tackle on classical computers. A versatile optical dipole trap has been constructed and characterized. The trap can be converted to an optical lattice, allowing for the investigation of the phase diagram of the two-component, one-dimensional, imbalanced Fermi gas.
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    Spin-imbalance in a one-dimensional Fermi gas
    (Nature Publishing Group, 2010) Liao, Yean-an; Rittner, Ann Sophie C.; Paprotta, Tobias; Li, Wenhui; Partridge, Guthrie B.; Hulet, Randall G.; Baur, Stefan K.; Mueller, Erich J.; Rice Quantum Institute
    Superconductivity and magnetism generally do not coexist. Changing the relative number of up and down spin electrons disrupts the basic mechanism of superconductivity, where atoms of opposite momentum and spin form Cooper pairs. Nearly forty years ago Fulde and Ferrell [1] and Larkin and Ovchinnikov [2] (FFLO) proposed an exotic pairing mechanism in which magnetism is accommodated by the formation of pairs with finite momentum. Despite intense theoretical and experimental efforts, however, polarized superconductivity remains largely elusive [3]. Unlike the three-dimensional (3D) case, theories predict that in one dimension (1D) a state with FFLO correlations occupies a major part of the phase diagram [4, 5, 6, 7, 8, 9, 10, 11, 12]. Here we report experimental measurements of density profiles of a two-spin mixture of ultracold [6] Li atoms trapped in an array of 1D tubes (a system analogous to electrons in 1D wires). At finite spin imbalance, the system phase separates with an inverted phase profile, as compared to the 3D case. In 1D, we find a partially polarized core surrounded by wings which, depending on the degree of polarization, are composed of either a completely paired or a fully polarized Fermi gas. Our work paves the way to direct observation and characterization of FFLO pairing.