Controlling the group velocity of colliding atomic Bose-Einstein condensates with Feshbach resonances
Ranchu Mathew, Eite Tiesinga
We report on a proposal to change the group velocity upon colliding two atomic Bose-Einstein Condensates (BECs) in analogy to slowing of light passing through dispersive media. We make use of ultracold collisions near a magnetic Feshbach resonance, which gives rise to a sharp variation in scattering length with collision energy and thereby changes the group velocity. A generalized Gross-Pitaveskii equation is derived for a small BEC moving through a larger stationary BEC. We denote the two condensates by laser and medium BEC, respectively, to highlight the analogy to a laser pulse travelling through a medium. We derive an expression for the group velocity for a homogeneous medium as well as for the difference in distance, \delta, covered by the laser BEC in the presence and absence of a finite-sized medium BEC. For a medium and laser of the same isotopic species, the shift $\delta$ has an upper bound of twice the Thomas-Fermi radius of the medium. For typical narrow Feshbach resonances and a medium with number density 10^14} cm^-3} up to 85% of the upper bound can be achieved, making the effect experimentally observable. We also derive constraints on the experimental realization of our proposal.
Physical Review A (Atomic, Molecular and Optical Physics)
and Tiesinga, E.
Controlling the group velocity of colliding atomic Bose-Einstein condensates with Feshbach resonances, Physical Review A (Atomic, Molecular and Optical Physics), [online], https://doi.org/10.1103/PhysRevA.87.053608, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=913087
(Accessed December 7, 2023)