Field Theory for Trapped Atomic Gases

Henk T. C. Stoof

W. Geist

Peter Federsel, Carola Rogulj, Tobias Menold +2 more

Microwave fields can be used to drive local spin transitions in quantum gases and for outcoupling of cold atomic beams from magnetic traps. In this paper, we derive an analytic theory for the outcoupling rate as a response to weak microwave fields of varying frequency and power. The theory holds for thermal clouds and Bose-Einstein condensates. It allows for calculating transition rates in arbitrary magnetic trap geometries and includes the effect of gravity. We verify our theory by measuring the flux of outcoupled atoms at the single-particle level. The derived spectral response is important for magnetic noise spectroscopy with quantum gases, and for probing quantum gas dynamics with single atom detectors in real time.

N. Dupuis

Henk T. C. Stoof

Matthew Wingate A

Trapped and cooled gases of alkali atoms can be manipulated to exhibit a variety of interesting phenomena.For example, dilute gases of fermionic atoms, in 2 hyperfine states, can be cooled to temperatures where they become superfluid.An external field can be applied to tune the scattering length a.When |a| exceeds the interparticle spacing, nonperturbative tools are needed to study the system theoretically.The unitary limit, |a| → ∞, is particularly interesting due to its universality and symmetry.Lattice field theory and effective field theory can be used to systematically calculate properties of this system.Results are presented for the finite temperature phase transition and for behavior near zero temperature.