10 research outputs found
Dynamics of quantum quenching for BCS-BEC systems in the shallow BEC regime
The problem of coupled Fermi-Bose mixtures of an ultracold gas near a narrow
Feshbach resonance is approached through the time-dependent and complex
Ginzburg-Landau (TDGL) theory. The dynamical system is constructed using
Ginzburg-Landau-Abrikosov-Gor'kov (GLAG) path integral methods with the single
mode approximation for the composite Bosons, and the equilibrium states are
obtained in the BEC regime for adiabatic variations of the Feshbach detuning
along the stationary solutions of the dynamical system. Investigations into the
rich superfluid dynamics of this system in the shallow BEC regime yields the
onset of multiple interference patterns in the dynamics as the system is
quenched from the deep-BEC regime. This results in a partial collapse and
revival of the coherent matter wave field of the BEC, whose temporal profile is
reported.Comment: 24 pages, 7 figures. Submitted to European Journal of Physics Plu
An ansatz for the nonlinear Demkov-Kunike problem for cold molecule formation
We study nonlinear mean-field dynamics of ultracold molecule formation in the
case when the external field configuration is defined by the level-crossing
Demkov-Kunike model, characterized by a bell-shaped coupling and finite
variation of the detuning. Analyzing the fast sweep rate regime of the strong
interaction limit, which models a situation when the peak value of the coupling
is large enough and the resonance crossing is sufficiently fast, we construct a
highly accurate ansatz to describe the temporal dynamics of the molecule
formation in the mentioned interaction regime. The absolute error of the
constructed approximation is less than 3*10^-6 for the final transition
probability while at certain time points it might increase up to 10^-3.
Examining the role of the different terms in the constructed approximation, we
prove that in the fast sweep rate regime of the strong interaction limit the
temporal dynamics of the atom-molecule conversion effectively consists of the
process of resonance crossing, which is governed by a nonlinear equation,
followed by atom-molecular coherent oscillations which are basically described
by a solution of the linear problem, associated with the considered nonlinear
one.Comment: Accepted for publication in J. Contemp. Phys. (Armenian National
Academy of Sciences) 8 pages, 4 figure
Achieving high molecular conversion efficiency via a magnetic field pulse train
We investigate the process of production of ultracold molecules in an ultracold bosonic system with particle interaction via designing a magnetic field pulse train near a Feshbach resonance. This technique offers a high conversion efficiency up to 100% by tuning the pulse durations appropriately. The molecular conversion efficiency is related to the duration of each pulse, which can be derived analytically. It is found that the conversion efficiency is insensitive to the first pulse, highly sensitive to the second one, and very insensitive to the third one. The effects of particle interaction on conversion process are discussed as well.Physics, Condensed MatterSCI(E)EI0ARTICLE6null8