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Frontiers in Optics

Probing Fermi Degeneracy in Neutral Atomic 40K on an Atom Chip

M. Extavour, S. Aubin, Lindsay J. LeBlanc, Stefan H. Myrskog, Thorsten Schumm, David C. McKay, B. Cieslak, A. Stummer, Joseph H. Thywissen

Published Jan 1, 2006• 0 citations
Publisher

Abstract

We present recent results on achieving a degenerate Fermi gas (DFG) of neutral 40K via rapid 87Rb sympathetic cooling on an atom chip. We outline current work on interference and density-density correlation measurements in DFGs.
DOI
10.1364/fio.2006.ftux5

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We review our recent and ongoing work with Fermi gases on an atom chip. After reviewing some statistical and thermodynamic properties of the ideal, non-interacting Fermi gas, and a brief description of our atom chip and its capabilities, we discuss our experimental approach to producing a potassium-40 degenerate Fermi gas (DFG) using sympathetic cooling by a rubidium-87 Bose-Einstein condensate on an atom chip. In doing so, we describe the factors affecting the loading efficiency of the atom chip microtrap. This is followed by a discussion of species selectivity in radio frequency manipulation of the Bose-Fermi mixture, which we explore in the context of sympathetic evaporative cooling and radio-frequency dressed adiabatic double-well potentials. Next, we describe the incorporation of a crossed-beam dipole trap into the atom chip setup, in which we generate and manipulate strongly interacting spin mixtures of potassium-40. Finally, we conclude with a brief discussion of future research directions with DFGs and atom chips.
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We have produced a quantum degenerate 6Li^{6}\mathrm{L}\mathrm{i}6Li Fermi gas with up to $7\ifmmode\times\else\texttimes\fi{}{10}^{7}$ atoms, an improvement by a factor of 50 over all previous experiments with degenerate Fermi gases. This was achieved by sympathetic cooling with bosonic 23Na^{23}\mathrm{N}\mathrm{a}23Na in the F=2F=2F=2, upper hyperfine ground state. We have also achieved Bose-Einstein condensation of F=2F=2F=2 sodium atoms by direct evaporation.
Abstract We review the status of cooling techniques aimed at achieving the deepest quantum degeneracy for atomic Fermi gases. We first discuss some physics motivations, providing a quantitative assessment of the need for deep quantum degeneracy in relevant physics cases, such as the search for unconventional superfluid states. Attention is then focused on the most widespread technique to reach deep quantum degeneracy for Fermi systems, sympathetic cooling of Bose–Fermi mixtures, organizing the discussion according to the specific species involved. Various proposals to circumvent some of the limitations on achieving the deepest Fermi degeneracy, and their experimental realizations, are then reviewed. Finally, we discuss the extension of these techniques to optical lattices and the implementation of precision thermometry crucial to the understanding of the phase diagram of classical and quantum phase transitions in Fermi gases.
We discuss experiments to produce and detect atom correlations in a degenerate or nearly degenerate gas of neutral atoms. First we treat the atomic analog of the celebrated Hanbury Brown Twiss experiment, in which atom correlations result simply from interference effects without any atom interactions. We have performed this experiment for both bosons and fermions. Next we show how atom interactions produce correlated atoms using the atomic analog of spontaneous four‐wave mixing. Finally, we briefly mention experiments on a one dimensional gas on an atom chip in which correlation effects due to both interference and interactions have been observed.