The Different Temperature-Dependent Behaviors of Dark Solitons in Fermi Superfluid Gases Along the BCS–BEC Crossover

We studied the temperature-dependent behavior of dark solitons in superfluid Fermi gases along the BCS–BEC crossover by solving the finite-temperature Bogoliubov-de Gennes equations. The notch depth of the soliton density distribution decreases with the increase in temperature in the whole BCS–BEC crossover. In particular, the notch depth has an obvious different temperature-dependent behavior from the BCS regime to the BEC regime, i.e, it has a concave function in the BCS regime, linear function in the unitary regime and convex function in the BEC regime.