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Fermion Pairing across a Dipolar Interaction Induced Resonance
It is known from the solution of the two-body problem that an anisotropic
dipolar interaction can give rise to s-wave scattering resonances, which are
named as dipolar interaction induced resonaces (DIIR). In this letter, we study
zero-temperature many-body physics of a two-component Fermi gas across a DIIR.
In the low-density regime, it is very striking that the resulting pairing order
parameter is a nearly isotropic singlet pairing and the physics can be well
described by an s-wave resonant interaction potential with finite range
corrections, despite of the anisotropic nature of dipolar interaction. The
pairing energy is as strong as a unitary Fermi gas nearby a magnetic Feshbach
resonance. In the high density regime, the anisotropic effect plays an
important role. We find phase transitions from singlet pairing to a state with
mixed singlet and triplet pairing, and then from mixed pairing to pure triplet
pairing. The state with mixed pairing spontaneously breaks the time-reversal
symmetry.Comment: 4.5 pages, 4 figures, figures updated, minor changes in tex
s-Wave Scattering Resonances Induced by Dipolar Interactions of Polar Molecules
We show that s-wave scattering resonances induced by dipolar interactions in
a polar molecular gas have a universal large and positive effective range,
which is very different from Feshbach resonances realized in cold atoms before,
where the effective range is either negligible or negative. Such a difference
has important consequence in many-body physics. At high temperature regime, a
positive effective range gives rise to stronger repulsive interaction energy
for positive scattering length, and weaker attractive interaction energy for
negative scattering length. While at low-temperatures, we study polaron problem
formed by single impurity molecule, and we find that the polaron binding energy
increases at the BEC side and decreases at the BCS side. All these effects are
in opposite to narrow Feshbach resonances where the effective range is
negative.Comment: 5 pages, 3 figures, published versio
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