The Fermi Gases and Superfluids

Yi Yu, Qijin Chen

Martin W. Zwierlein

Abstract This chapter reviews experimental studies of fermionic superfluidity in ultracold atomic gases. Scattering properties of ultracold atoms and Feshbach resonances are introduced. The basic theoretical framework is presented based on the Leggett ansatz that provides intuition into many of the observed phenomena. The various experimental observations related to fermion pair condensation and superfluidity are described. The thermodynamic measurements of strongly interacting Fermi gases are considered. Experiments on superfluidity in the presence of population imbalance are reviewed. These studies have led to the observation of the Clogston–Chandrasekhar (or Pauli) limit of fermionic superfluidity and to the identification of a novel attractive Fermi liquid of polaronic quasiparticles. Novel Fermi systems, such as Fermi gases in lower dimensions, optical lattices, dipolar Fermi gases, and spin–orbit coupled Fermi gases, are also touched on briefly.

Xiu-Ying Qi, Ai‐Xia Zhang, Ju-Kui Xue

We present an analytical study on the dynamics of dark solitons in superfluid Fermi gases. By using the modified lens-type transformation, the dynamical equation of superfluid Fermi gases is reduced to a modified one-dimensional nonlinear Shorödinger equation (NLSE). Once again, by using the reductive perturbation method, the NLSE is reduced to a standard Korteweg-de Vries equation which may be useful for understanding the dynamics of dark solitons in superfluid Fermi gases. The existence of dark soliton solutions in the Fermi gases is provided. In particular, we show that, by manipulating and controlling the scattering length between Fermi atomics of different components and the external potential, the soliton's parameters (amplitude and width) can be changed in a controllable way.

Zygmunt M. Galasiewicz