Abstract
We report the equilibrium vortex phase diagram of a rotating two-band Fermi gas confined to a cylindrically symmetric parabolic trapping potential, using the recently developed finite-temperature effective field theory (Klimin et al 2016 Phys. Rev. A 94 023620). A non-monotonic resonant dependence of the free energy as a function of the temperature and the rotation frequency is revealed for a two-band superfluid. We particularly focus on novel features that appear as a result of interband interactions and can be experimentally resolved. The resonant dependence of the free energy is directly manifested in vortex phase diagrams, where areas of stability for both integer and fractional vortex states are found. The study embraces the BCS–BEC crossover regime and the entire temperature range below the critical temperature Tc. Significantly different behavior of vortex matter as a function of the interband coupling is revealed in the BCS and BEC regimes.
Highlights
Quantum gases constitute a remarkable testing ground for the theory of the superfluid state and its various macroscopic excitations, such as vortices and solitons
Vortices are stabilized in an atomic gas by rotating the gas, just as vortices in superconductors can be stabilized by a magnetic field: the Coriolis force acts on a particle in a rotating frame of reference in the same way as the Lorentz force acts on a charged particle in a magnetic field [1]
To vortex phase diagrams for a one-band Fermi gas [12, 14, 15], the boundaries of the areas of stability for different vortex configurations exhibit a non-monotonic dependence on the rotation frequency and a reentrant behavior as a function of the temperature
Summary
Quantum gases constitute a remarkable testing ground for the theory of the superfluid state and its various macroscopic excitations, such as vortices and solitons. Vortices and many-vortex states in rotating trapped superfluid Fermi gases have become a subject of an intense experimental [2,3,4,5] and theoretical [6,7,8,9,10,11,12,13,14,15] research during last two decades Since recently, this line of research has become of particular interest in multicomponent quantum systems. In this work, the subject of our interest are fractional vortices in two-band Fermi gases of ultracold atoms in the BCS-BEC crossover. The stability of different vortex states in a rotating trapped one-band Fermi gas has been theoretically studied in Refs.
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