4,312 research outputs found
Antiferromagnetism and superfluidity of a dipolar Fermi gas in a 2D optical lattice
In a dipolar Fermi gas, the dipole-dipole interaction between fermions can be
turned into a dipolar Ising interaction between pseduospins in the presence of
an AC electric field. When trapped in a 2D optical lattice, such a dipolar
Fermi gas has a very rich phase diagram at zero temperature, due to the
competition between antiferromagnetism and superfluidity. At half filling, the
antiferromagnetic state is the favored ground state. The superfluid state
appears as the ground state at a smaller filling factor. In between there is a
phase-separated region. The order parameter of the superfluid state can display
different symmetries depending on the filling factor and interaction strength,
including d-wave (), extend s-wave (), or their linear combination
(). The implication for the current experiment is discussed.Comment: 11 pages, 3 figures, references update
Critical temperature of pair condensation in a dilute Bose gas with spin-orbit coupling
We study the Bardeen-Cooper-Shrieffer (BCS) pairing state of a two-component
Bose gas with a symmetric spin-orbit coupling. In the dilute limit at low
temperatures, this system is essentially a dilute gas of diatomic molecules. We
compute the effective mass of the molecule and find that it is anisotropic in
momentum space. The critical temperature of the pairing state is about eight
times smaller than the Bose-Einstein condensation (BEC) transition temperature
of an ideal Bose gas with the same density.Comment: 7 pages, 1 figur
The three-body recombination of a condensed Bose gas near a Feshbach resonance
In this paper, we study the three-body recombination rate of a homogeneous
dilute Bose gas with a Feshbach resonance at zero temperature. The ground state
and excitations of this system are obtained. The three-body recombination in
the ground state is due to the break-up of an atom pair in the quantum
depletion and the formation of a molecule by an atom from the broken pair and
an atom from the condensate. The rate of this process is in good agreement with
the experiment on Na in a wide range of magnetic fields.Comment: 10 pages, 2 figures, to be published in Phys. Rev.
Induced interaction in a spin-polarized Fermi gas
We study the effect of the induced interaction on the superfluidtransition
temperature of a spin-polarized Fermi gas. In the BCS limit, the polarization
is very small in the superfluid state, and the effect of the induced
interaction is almost the same as in the spin-balanced case. The temperature Tt
and the polarization Pt of the tricritical point are both reduced from
mean-field results by a factor about 2.22. This reduction is also significant
beyond the BCS limit. In the unitary limit, we find (Pt,Tt/TF)=(0.42,0.16), in
comparison with mean-field and experimental results.Comment: 6 pages, 2 figure
Collinear antiferromagnetic state in a two-dimensional Hubbard model at half filling
In a half-filled Hubbard model on a square lattice, the next-nearest-neighbor
hopping causes spin frustration, and the collinear antiferromagnetic (CAF)
state appears as the ground state with suitable parameters. We find that there
is a metal-insulator transition in the CAF state at a critical on-site
repulsion. When the repulsion is small, the CAF state is metallic, and a van
Hove singularity can be close to the Fermi surface, resulting in either a kink
or a discontinuity in the magnetic moment. When the on-site repulsion is large,
the CAF state is a Mott insulator. A first-order transition from the CAF phase
to the antiferromagnetic phase and a second-order phase transition from the CAF
phase to the paramagnetic phase are obtained in the phase diagram at zero
temperature.Comment: 5 pages, 5 figures, two column
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