10,086 research outputs found
A self-consistent theory of atomic Fermi gases with a Feshbach resonance at the superfluid transition
A self-consistent theory is derived to describe the BCS-BEC crossover for a
strongly interacting Fermi gas with a Feshbach resonance. In the theory the
fluctuation of the dressed molecules, consisting of both preformed Cooper-pairs
and ``bare'' Feshbach molecules, has been included within a self-consistent
-matrix approximation, beyond the Nozi\`{e}res and Schmitt-Rink strategy
considered by Ohashi and Griffin. The resulting self-consistent equations are
solved numerically to investigate the normal state properties of the crossover
at various resonance widths. It is found that the superfluid transition
temperature increases monotonically at all widths as the effective
interaction between atoms becomes more attractive. Furthermore, a residue
factor of the molecule's Green function and a complex effective mass have
been determined, to characterize the fraction and lifetime of Feshbach
molecules at . Our many-body calculations of agree qualitatively
well with the recent measurments on the gas of Li atoms near the broad
resonance at 834 Gauss. The crossover from narrow to broad resonances has also
been studied.Comment: 6 papes, 6 figure
Topological superfluid in one-dimensional spin-orbit coupled atomic Fermi gases
ARC Centre of Excellence for Quantum-Atom Optics, Centre for Atom Optics and
Ultrafast Spectroscopy, Swinburne University of Technology, Melbourne 3122,
AustraliaComment: 7 pages, 8 figures; submitted to Physical Review
On the renormalization of quasi parton distribution
Recent developments showed that light-cone parton distributions can be
studied by investigating the large momentum limit of the hadronic matrix
elements of spacelike correlators, which are known as quasi parton
distributions. Like a light-cone parton distribution, a quasi parton
distribution also contains ultraviolet divergences and therefore needs
renormalization. The renormalization of non-local operators in general is not
well understood. However, in the case of quasi quark distribution, the bilinear
quark operator with a straight-line gauge link appears to be multiplicatively
renormalizable by the quark wave function renormalization in the axial gauge.
We first show that the renormalization of the self energy correction to the
quasi quark distribution is equivalent to that of the heavy-light quark vector
current in heavy quark effective theory at one-loop order. Assuming this
equivalence at two-loop order, we then show that the multiplicative
renormalizability of the quasi quark distribution is true at two-loop order.Comment: 14 pages, 4 figure
First and second sound in a two-dimensional dilute Bose gas across the Berezinskii-Kosterlitz-Thouless transition
We theoretically investigate first and second sound of a two-dimensional (2D)
atomic Bose gas in harmonic traps by solving Landau's two-fluid hydrodynamic
equations. For an isotropic trap, we find that first and second sound modes
become degenerate at certain temperatures and exhibit typical avoided crossings
in mode frequencies. At these temperatures, second sound has significant
density fluctuation due to its hybridization with first sound and has a
divergent mode frequency towards the Berezinskii-Kosterlitz-Thouless (BKT)
transition. For a highly anisotropic trap, we derive the simplified
one-dimensional hydrodynamic equations and discuss the sound-wave propagation
along the weakly confined direction. Due to the universal jump of the
superfluid density inherent to the BKT transition, we show that the first sound
velocity exhibits a kink across the transition. Our predictions can be readily
examined in current experimental setups for 2D dilute Bose gases.Comment: 5 pages, 4 figure
Topological Fulde-Ferrell superfluid in spin-orbit coupled atomic Fermi gases
We theoretically predict a new topological matter - topological inhomogeneous
Fulde-Ferrell superfluid - in one-dimensional atomic Fermi gases with equal
Rashba and Dresselhaus spin-orbit coupling near s-wave Feshbach resonances. The
realization of such a spin-orbit coupled Fermi system has already been
demonstrated recently by using a two-photon Raman process and the extra
one-dimensional confinement is easy to achieve using a tight two-dimensional
optical lattice. The topological Fulde-Ferrell superfluid phase is
characterized by a nonzero center-of-mass momentum and a non-trivial Berry
phase. By tuning the Rabi frequency and the detuning of Raman laser beams, we
show that such an exotic topological phase occupies a significant part of
parameter space and therefore it could be easily observed experimentally, by
using, for example, momentum-resolved and spatially resolved radio-frequency
spectroscopy.Comment: 5 pages, 4 figure
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