Browsing by Author "Fry, Jacob A."

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    1D to 3D Crossover of a Spin-Imbalanced Fermi Gas
    (American Physical Society, 2016) Revelle, Melissa C.; Fry, Jacob A.; Olsen, Ben A.; Hulet, Randall G.; Rice Center for Quantum Materials
    We have characterized the one-dimensional (1D) to three-dimensional (3D) crossover of a two-component spin-imbalanced Fermi gas of 6Li atoms in a 2D optical lattice by varying the lattice tunneling and the interactions. The gas phase separates, and we detect the phase boundaries using in situ imaging of the inhomogeneous density profiles. The locations of the phases are inverted in 1D as compared to 3D, thus providing a clear signature of the crossover. By scaling the tunneling rate t with respect to the pair binding energy εB, we observe a collapse of the data to a universal crossover point at a scaled tunneling value of ˜tc=0.025(7).
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    Phase diagram of a strongly interacting spin-imbalanced Fermi gas
    (American Physical Society, 2015) Olsen, Ben A.; Revelle, Melissa C.; Fry, Jacob A.; Sheehy, Daniel E.; Hulet, Randall G.; Rice Center for Quantum Materials
    We obtain the phase diagram of spin-imbalanced interacting Fermi gases from measurements of density profiles of Li6 atoms in a harmonic trap. These results agree with, and extend, previous experimental measurements. Measurements of the critical polarization at which the balanced superfluid core vanishes generally agree with previous experimental results and with quantum Monte Carlo (QMC) calculations in the Bardeen-Cooper-Schrieffer and unitary regimes. We disagree with the QMC results in the Bose-Einstein condensate regime, however, where the measured critical polarizations are greater than theoretically predicted. We also measure the equation of state in the crossover regime for a gas with equal numbers of the two fermion spin states.
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    Spin-imbalanced ultracold Fermi gases in a two-dimensional array of tubes
    (American Physical Society, 2020) Sundar, Bhuvanesh; Fry, Jacob A.; Revelle, Melissa C.; Hulet, Randall G.; Hazzard, Kaden R.A.; Rice Center for Quantum Materials
    Motivated by a recent experiment Revelle et al., [Phys. Rev. Lett. 117, 235301 (2016)] that characterized the one- to three-dimensional crossover in a spin-imbalanced ultracold gas of 6Li atoms trapped in a two-dimensional array of tunnel-coupled tubes, we calculate the phase diagram for this system by using Hartree-Fock Bogoliubov-de Gennes mean-field theory and compare the results with experimental data. Mean-field theory predicts fully-spin-polarized normal, partially-spin-polarized normal, spin-polarized superfluid, and spin-balanced superfluid phases in a homogeneous system. We use the local density approximation to obtain density profiles of the gas in a harmonic trap. We compare these calculations with experimental measurements in Revelle et al. as well as previously unpublished data. Our calculations qualitatively agree with experimentally measured densities and coordinates of the phase boundaries in the trap and quantitatively agree with experimental measurements at moderate-to-large polarizations. Our calculations also reproduce the experimentally observed universal scaling of the phase boundaries for different scattering lengths at a fixed value of scaled intertube tunneling. However, our calculations have quantitative differences with experimental measurements at low polarization and fail to capture important features of the one- to three-dimensional crossover observed in experiments. These suggest the important role of physics beyond mean-field theory in the experiments. We expect that our numerical results will aid future experiments in narrowing the search for the Fulde-Ferrell-Larkin-Ovchinnikov phase.