Berlin 2005 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 23: Posters Superconductivity, Solids at Low Temperature

TT 23.58: Poster

Montag, 7. März 2005, 14:00–18:00, Poster TU D

Josephson effects in cold atomic fermionic gases near a Feshbach resonance — •Flavio Nogueira — Institut für Theoretische Physik, Freie Universität Berlin

The Josephson effects that emerge out of a system featuring two fermionic atomic gases in contact through a weak link is considered. The subsystems are assumed to be near a Feshbach resonance. The results will be derived both microscopically and phenomenologically. In the Josephson current appears three types of phase differences: (i) a phase difference Δθ=θ₁−θ₂ corresponding to the phases θ₁ and θ₂ of the molecular bosons of subsystems 1 and 2, respectively; (ii) a phase difference Δϕ=ϕ₁−ϕ₂, corresponding to the phases ϕ₁ and ϕ₂ of the Cooper pairs of of subsystems 1 and 2, respectively; (iii) and a phase difference between molecular bosons and Cooper pairs across the link. The time dependence of the phase difference between molecules can be controlled by the detuning parameter. While for Δϕ the familiar Josephson time evolution holds, i.e., dΔϕ/dt=2Δµ, where Δµ=µ₁−µ₂ is the difference between the chemical potentials, we obtain dΔθ/dt=2Δµ+Δδ, where δ₁−δ₂ is the detuning difference. This type of effect may be used experimentally to probe the presence of Cooper pairs in the system by controlling the BCS-BEC crossover.