Superfluid/ferromagnet/superfluid-junction and $π$ -phase in a superfluid Fermi gas at finite temperaturesSuperfluid/ferromagnet/superfluid-junction and $π$-phase in a superfluid Fermi gas at finite temperatures

Takashi Kashimura, Shunji Tsuchiya, Yoji Ohashi

We investigate the stability of $π$ -phase in a polarized superfluid Fermi gas ( $N_\uparrow>N_\downarrow$ , where $N_σ$ is the number of atoms in the hyperfine state described by pseudospin- $σ$ ). In our previous paper [T. Kashimura, S. Tsuchiya, and Y. Ohashi, Phys. Rev. A {\bf 82}, 033617 (2010)], we showed that excess atoms ( $ΔN=N_\uparrow-N_\downarrow$ ) localized around a potential barrier embedded in the system induces the $π$ -phase at T=0, where the phase of superfluid order parameter differ by $π$ across the junction. In this paper, we extend our previous work to include temperature effects within the mean-field theory. We show that the $π$ -phase is stable even at finite temperatures, although transition from the $π$ -phase to 0-phase eventually occurs at a certain temperature. Our results indicate that the $π$ -phase is experimentally accessible in cold Fermi gases.We investigate the stability of $π$-phase in a polarized superfluid Fermi gas ($N_\uparrow>N_\downarrow$, where $N_σ$ is the number of atoms in the hyperfine state described by pseudospin-$σ$). In our previous paper [T. Kashimura, S. Tsuchiya, and Y. Ohashi, Phys. Rev. A {\bf 82}, 033617 (2010)], we showed that excess atoms ($ΔN=N_\uparrow-N_\downarrow$) localized around a potential barrier embedded in the system induces the $π$-phase at T=0, where the phase of superfluid order parameter differ by $π$ across the junction. In this paper, we extend our previous work to include temperature effects within the mean-field theory. We show that the $π$-phase is stable even at finite temperatures, although transition from the $π$-phase to 0-phase eventually occurs at a certain temperature. Our results indicate that the $π$-phase is experimentally accessible in cold Fermi gases.

arXiv:1107.0105Jul 1, 20110 citations

Superfluidity in atomic Fermi gases

Yi Yu, Qijin Chen

arXiv:1101.2846Physica C SuperconductivityNov 7, 20093 citations

Aspects of superfluid cold atomic gases in optical lattices

Gentaro Watanabe A, Sukjin Yoon

We review our studies on Bose and Fermi superfluids of cold atomic gases in optical lattices at zero temperature. Especially, we focus on superfluid Fermi gases along the crossover between the Bardeen-Cooper-Schrieffer (BCS) and the Bose-Einstein condensate (BEC) states, which enable us to study the Bose and the Fermi superfluids in a unified point of view. We discuss basic static and long-wavelength properties (such as the equation of state, incompressibility, and effective mass), energetic stability, and energy band structures of the superfluid Fermi gases in an optical lattice periodic along one spatial direction. The periodic potential causes pairs of atoms to be strongly bound, and this can affect the static and long-wavelength properties and the stability of the superflow. Regarding the band structure, a peculiar loop structure called “swallowtail” can appear in superfluid Fermi gases and in the Bose case, but the mechanism of emergence in the Fermi case is very different from that in bosonic case. Other quantum phases that the cold atomic gases in optical lattices can show are also briefly discussed based on their roles as quantum simulators of Hubbard models.We review our studies on Bose and Fermi superfluids of cold atomic gases in optical lattices at zero temperature. Especially, we focus on superfluid Fermi gases along the crossover between the Bardeen-Cooper-Schrieffer (BCS) and the Bose-Einstein condensate (BEC) states, which enable us to study the Bose and the Fermi superfluids in a unified point of view. We discuss basic static and long-wavelength properties (such as the equation of state, incompressibility, and effective mass), energetic stability, and energy band structures of the superfluid Fermi gases in an optical lattice periodic along one spatial direction. The periodic potential causes pairs of atoms to be strongly bound, and this can affect the static and long-wavelength properties and the stability of the superflow. Regarding the band structure, a peculiar loop structure called “swallowtail” can appear in superfluid Fermi gases and in the Bose case, but the mechanism of emergence in the Fermi case is very different from that in bosonic case. Other quantum phases that the cold atomic gases in optical lattices can show are also briefly discussed based on their roles as quantum simulators of Hubbard models.

arXiv:1301.3363Journal of the Korean Physical SocietyAug 1, 20135 citations

Superfluid/ferromagnet/superfluid-junction and

π

-phase in a superfluid Fermi gas at finite temperatures

We investigate the stability of

π

-phase in a polarized superfluid Fermi gas (

N_\uparrow>N_\downarrow

, where

N_σ

is the number of atoms in the hyperfine state described by pseudospin-

σ

). In our previous paper [T. Kashimura, S. Tsuchiya, and Y. Ohashi, Phys. Rev. A {\bf 82}, 033617 (2010)], we showed that excess atoms (

ΔN=N_\uparrow-N_\downarrow

) localized around a potential barrier embedded in the system induces the

π

-phase at T=0, where the phase of superfluid order parameter differ by

π

across the junction. In this paper, we extend our previous work to include temperature effects within the mean-field theory. We show that the

π

-phase is stable even at finite temperatures, although transition from the

π

-phase to 0-phase eventually occurs at a certain temperature. Our results indicate that the

π

-phase is experimentally accessible in cold Fermi gases.