Traveling Dark Solitons in Superfluid Fermi Gases

Families of dark solitons exist in superfluid Fermi gases. The energy-velocity dispersion and number of depleted particles completely determines the dynamics of dark solitons on a slowly-varying background density. For the unitary Fermi gas we determine these relations from general scaling arguments and conservation of local particle number. We find solitons to oscillate sinusoidally at the trap frequency reduced by a factor of $1/\sqrt{3}$. Numerical integration of the time-dependent Bogoliubov-de Gennes equation determines spatial profiles and soliton dispersion relations across the BEC-BCS crossover and proves consistent with the scaling relations at unitarity.Comment: Small changes in response to referee's comments; fig 1 revised and refs updated. Cross listed to nucl-th due to interest in the unitary Fermi ga

Pairing in Asymmetrical Fermi Systems with Intra- and Inter-Species Correlations

We consider inter- and intra-species pairing interactions in an asymmetrical Fermi system. Using equation of motion method, we obtain coupled mean-field equations for superfluid gap functions and population densities. We construct a phase diagram across BCS-BEC regimes. Due to intra-species correlations, the BCS singlet superfluid state can sustain finite polarizations, $P$. For larger $P$, we find phase separations in BCS and BEC regimes. A superfluid phase exists for all $P$ deep in BEC regime. Our results may apply to pairing in ultracold fermions, nuclear and quark matter physics.Comment: Contents revised. Added reference

Tuning the Tricritical Point with Spin-orbit Coupling in Polarized Fermionic Condensates

We investigate a two-component atomic Fermi gas with population imbalance in the presence of Rashba-type spin-orbit coupling (SOC). As a competition between SOC and population imbalance, the finite-temperature phase diagram reveals a large varieties of new features, including the expanding of the superfluid state regime and the shrinking of both the phase separation and the normal regimes. For sufficiently strong SOC, the phase separation region disappears, giving way to the superfluid state. We find that the tricritical point moves toward regime of low temperature, high magnetic field, and high polarization as the SOC increases.Comment: 4 pages, 5 figure

Medium effects close to s- and p-wave Feshbach resonances in atomic Fermi gases

Many-body effects may influence properties, such as scattering parameters, nature of pairing, etc., close to a Feshbach resonance in the fermion BEC-BCS crossover problem. We study effects such as these using a tractable crossing-symmetric approach. This method allow us to include quantum fluctuations, such as, density, current, spin, spin-current and the higher-order fluctuations in a self-consistent fashion. The underlying fermion interaction is reflected in the "driving" term. We perform calculations here on both Bose-Einstein condensate (BEC) and BCS sides, and taking the driving term to be finite range, and of arbitrary strength. These are related to two-body singlet and triplet scattering parameters, and can be connected with experimental s- and p-wave Feshbach resonances. We include the $\ell=0$ density and spin fluctuations, as well as $\ell=1$ current and spin-current fluctuations. We calculate renormalized scattering amplitudes, pairing amplitudes, nature of pairing, etc., on both the BEC and BCS sides. We then compare our results qualitatively with experiments.Comment: 6 pages, 7 figures. arXiv admin note: text overlap with arXiv:cond-mat/0607045 by other author