Vortex-Antivortex Lattice in Ultracold Fermionic Gases

Abstract

We discuss ultracold Fermi gases in two dimensions, which could be realized in a strongly confining one-dimensional optical lattice. We obtain the temperature versus effective interaction phase diagram for an s-wave superfluid and show that, below a certain critical temperature Tc, spontaneous vortex-antivortex pairs appear for all coupling strengths. In addition, we show that the evolution from weak-to-strong coupling is smooth, and that the system forms a square vortex-antivortex lattice at a lower critical temperature TM.

Finite-temperature phase diagram of quasi-two-dimensional imbalanced Fermi gases beyond mean field

“…[11], and 0.125 in Refs. [10] and [12]. Monte Carlo simulations give T c /ǫ F ≈ 0.1 for |ǫ B |/ǫ F = 10 [35].…”

“…We find that the transition temperature is reduced by a factor ≈ 2.72, in the case of a balanced Fermi system, and the temperature and polarization of the tricritical point of imbalanced same factor as a function of |ǫ B |/µ, in comparison to the MF results. It is worth mentioning that in the BEC region the universal behavior found for the transition temperature in 2D fermionic systems, considering the phase fluctuation effects [10][11][12], is that the transition temperature obeys a behavior which may be expressed qualitatively in the form T c /ǫ F ≈ const × tanh(|ǫ B |/ǫ F ), reaching a limiting value for large |ǫ B |/ǫ F . The value of the constant is 0.075 in Ref.…”

“…By taking into account the phase fluctuation effect, the BKT transition has been investigated in 2D balanced [10,11] as well as imbalanced systems [12]. In all these works a strong dependence of the BKT transition temperature T BKT on the two-body energy |e B | has been found.…”

“…In all these works a strong dependence of the BKT transition temperature T BKT on the two-body energy |e B | has been found. Below T BKT pairs of vortices and antivortices surge, and will eventually condense as the temperature is lowered [10][11][12].…”

Unconventional interaction between vortices in a polarized Fermi gas

“…[7] In addition, several theoretical studies have analyzed the possible new properties of vortices across a Feshbach resonance from the BCS to the BEC side. [8,9,10,11] The physics of atomic Fermi gases is also of fundamental interest beyond the standard BCS/BEC physics, owing to the new tuning flexibility in the atomic gas systems. Under the condition of density imbalance (hence mismatched Fermi surfaces) between the spin-up and -down fermions, a modulated Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) [12] superfluid phase, has long been theoretically anticipated.…”