5,184 research outputs found
A quasi-pure Bose-Einstein condensate immersed in a Fermi sea
We report the observation of co-existing Bose-Einstein condensate and Fermi
gas in a magnetic trap. With a very small fraction of thermal atoms, the 7Li
condensate is quasi-pure and in thermal contact with a 6Li Fermi gas. The
lowest common temperature is 0.28 muK = 0.2(1) T_C = 0.2(1) T_F where T_C is
the BEC critical temperature and T_F the Fermi temperature. Behaving as an
ideal gas in the radial trap dimension, the condensate is one-dimensional.Comment: 4 pages, 5 figure
Production of Long-Lived Ultracold Li2 Molecules from a Fermi gas
We create weakly-bound Li2 molecules from a degenerate two component Fermi
gas by sweeping a magnetic field across a Feshbach resonance. The atom-molecule
transfer efficiency can reach 85% and is studied as a function of magnetic
field and initial temperature. The bosonic molecules remain trapped for 0.5 s
and their temperature is within a factor of 2 from the Bose-Einstein
condensation temperature. A thermodynamical model reproduces qualitatively the
experimental findings
Formation of a Matter-Wave Bright Soliton
We report the production of matter-wave solitons in an ultracold lithium 7
gas. The effective interaction between atoms in a Bose-Einstein condensate is
tuned with a Feshbach resonance from repulsive to attractive before release in
a one-dimensional optical waveguide. Propagation of the soliton without
dispersion over a macroscopic distance of 1.1 mm is observed. A simple
theoretical model explains the stability region of the soliton. These
matter-wave solitons open fascinating possibilities for future applications in
coherent atom optics, atom interferometry and atom transport.Comment: 11 pages, 5 figure
Time-resolved observation of spin-charge deconfinement in fermionic Hubbard chains
Elementary particles such as the electron carry several quantum numbers, for
example, charge and spin. However, in an ensemble of strongly interacting
particles, the emerging degrees of freedom can fundamentally differ from those
of the individual constituents. Paradigmatic examples of this phenomenon are
one-dimensional systems described by independent quasiparticles carrying either
spin (spinon) or charge (holon). Here we report on the dynamical deconfinement
of spin and charge excitations in real space following the removal of a
particle in Fermi-Hubbard chains of ultracold atoms. Using space- and
time-resolved quantum gas microscopy, we track the evolution of the excitations
through their signatures in spin and charge correlations. By evaluating
multi-point correlators, we quantify the spatial separation of the excitations
in the context of fractionalization into single spinons and holons at finite
temperatures
Collective Oscillations of an Imbalanced Fermi Gas: Axial Compression Modes and Polaron Effective Mass
We investigate the low-lying compression modes of a unitary Fermi gas with
imbalanced spin populations. For low polarization, the strong coupling between
the two spin components leads to a hydrodynamic behavior of the cloud. For
large population imbalance we observe a decoupling of the oscillations of the
two spin components, giving access to the effective mass of the Fermi polaron,
a quasi-particle composed of an impurity dressed by particle-hole pair
excitations in a surrounding Fermi sea. We find , in agreement
with the most recent theoretical predictions.Comment: 4 pages, 4 figures, submitted to PR
Thermal and mechanical development of extremely high heat flux cooling modules based on jet array technology
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1997.Includes bibliographical references.by Rudy S. Dahbura.M.S
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