7,394 research outputs found
Evolution of Fermion Pairing from Three to Two Dimensions
We follow the evolution of fermion pairing in the dimensional crossover from
3D to 2D as a strongly interacting Fermi gas of Li atoms becomes confined
to a stack of two-dimensional layers formed by a one-dimensional optical
lattice. Decreasing the dimensionality leads to the opening of a gap in
radio-frequency spectra, even on the BCS-side of a Feshbach resonance. The
measured binding energy of fermion pairs closely follows the theoretical
two-body binding energy and, in the 2D limit, the zero-temperature mean-field
BEC-BCS theory.Comment: 5 pages, 4 figure
Spin-Injection Spectroscopy of a Spin-Orbit Coupled Fermi Gas
The coupling of the spin of electrons to their motional state lies at the
heart of recently discovered topological phases of matter. Here we create and
detect spin-orbit coupling in an atomic Fermi gas, a highly controllable form
of quantum degenerate matter. We reveal the spin-orbit gap via spin-injection
spectroscopy, which characterizes the energy-momentum dispersion and spin
composition of the quantum states. For energies within the spin-orbit gap, the
system acts as a spin diode. To fully inhibit transport, we open an additional
spin gap, thereby creating a spin-orbit coupled lattice whose spinful band
structure we probe. In the presence of s-wave interactions, such systems should
display induced p-wave pairing, topological superfluidity, and Majorana edge
states
Magnon Dispersion in the Field-Induced Magnetically Ordered Phase of TlCuCl3
The magnetic properties of the interacting dimer system TlCuCl3 are
investigated within a bond-operator formulation. The observed field-induced
staggered magnetic order perpendicular to the field is described as a Bose
condensation of magnons which are linear combinations of dimer singlet and
triplet modes. This technique accounts for the magnetization curve and for the
field dependence of the magnon dispersion curves observed by high-field neutron
scattering measurements.Comment: 4 pages, 4 figures, REVTeX
Long-Lived Ultracold Molecules with Electric and Magnetic Dipole Moments
We create fermionic dipolar NaLi molecules in their triplet ground
state from an ultracold mixture of Na and Li. Using
magneto-association across a narrow Feshbach resonance followed by a two-photon
STIRAP transfer to the triplet ground state, we produce
ground state molecules in a spin-polarized state. We observe a lifetime of
in an isolated molecular sample, approaching the -wave
universal rate limit. Electron spin resonance spectroscopy of the triplet state
was used to determine the hyperfine structure of this previously unobserved
molecular state.Comment: 5 pages, 5 figure
Scaling of gauge balls and static potential in the confinement phase of the pure U(1) lattice gauge theory
We investigate the scaling behaviour of gauge-ball masses and static
potential in the pure U(1) lattice gauge theory on toroidal lattices. An
extended gauge field action is used with and -0.5. Gauge-ball correlation
functions with all possible lattice quantum numbers are calculated. Most
gauge-ball masses scale with the non-Gaussian exponent .
The gauge-ball mass scales with the Gaussian value in the investigated range of correlation lengths. The static potential is
examined with Sommer's method. The long range part scales consistently with
but the short range part tends to yield smaller values of . The
-function, having a UV stable zero, is obtained from the running
coupling. These results hold for both values, supporting universality.
Consequences for the continuum limit of the theory are discussed.Comment: Contribution to the Lattice 97 proceedings, LaTeX, 3 pages, 3 figure
Retinal oscillations carry visual information to cortex
Thalamic relay cells fire action potentials that transmit information from
retina to cortex. The amount of information that spike trains encode is usually
estimated from the precision of spike timing with respect to the stimulus.
Sensory input, however, is only one factor that influences neural activity. For
example, intrinsic dynamics, such as oscillations of networks of neurons, also
modulate firing pattern. Here, we asked if retinal oscillations might help to
convey information to neurons downstream. Specifically, we made whole-cell
recordings from relay cells to reveal retinal inputs (EPSPs) and thalamic
outputs (spikes) and analyzed these events with information theory. Our results
show that thalamic spike trains operate as two multiplexed channels. One
channel, which occupies a low frequency band (<30 Hz), is encoded by average
firing rate with respect to the stimulus and carries information about local
changes in the image over time. The other operates in the gamma frequency band
(40-80 Hz) and is encoded by spike time relative to the retinal oscillations.
Because these oscillations involve extensive areas of the retina, it is likely
that the second channel transmits information about global features of the
visual scene. At times, the second channel conveyed even more information than
the first.Comment: 21 pages, 10 figures, submitted to Frontiers in Systems Neuroscienc
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