Dynamics of Atom-Molecule Interactions

We investigate the quantum many-body dynamics of ultracold atom−molecule conversion using a Floquet spin-boson model, where the periodic energy detuning between molecules and atomic pairs is utilized to explore various dynamical regimes. We find that the upper bound of the adiabatic driving frequency increases continuously with the strength of molecule−molecule interactions, indicating that many-body interactions are beneficial in meeting the requirement of the adiabatic condition, thereby facilitating the realization of adiabatic atom−molecule conversion. This enhancement of the fulfillment of the adiabatic condition is further evidenced by the stabilization of periodic oscillations in the mean molecule number over time, protected by these interactions, even when the frequency lies within the localized regime. Interestingly, in the diffusive regime, while the many-body interaction has little effect on the dynamical equilibrium of atom−molecule conversion, it significantly expands the diffusive regime. In the high-frequency limit, many-body interactions are found to completely suppress atom−molecule conversion. Our results shed light on how molecule−molecule interactions influence the boundaries between different dynamical regimes.We investigate the quantum many-body dynamics of ultracold atom−molecule conversion using a Floquet spin-boson model, where the periodic energy detuning between molecules and atomic pairs is utilized to explore various dynamical regimes. We find that the upper bound of the adiabatic driving frequency increases continuously with the strength of molecule−molecule interactions, indicating that many-body interactions are beneficial in meeting the requirement of the adiabatic condition, thereby facilitating the realization of adiabatic atom−molecule conversion. This enhancement of the fulfillment of the adiabatic condition is further evidenced by the stabilization of periodic oscillations in the mean molecule number over time, protected by these interactions, even when the frequency lies within the localized regime. Interestingly, in the diffusive regime, while the many-body interaction has little effect on the dynamical equilibrium of atom−molecule conversion, it significantly expands the diffusive regime. In the high-frequency limit, many-body interactions are found to completely suppress atom−molecule conversion. Our results shed light on how molecule−molecule interactions influence the boundaries between different dynamical regimes.

Frontiers of PhysicsJan 1, 20251 citation

NONLINEAR DYNAMICS OF ATOM–MOLECULE CONVERSION

Libin Fu, Jie Liu

Annual review of cold atoms and moleculesMar 31, 20140 citations

Ultracold bosonic atom–molecule conversion dynamics with a linearly chirped Gaussian pulse

Fu-Quan Dou, Lina Hu, Xiu-Niao Zhao +2 more

We investigate the conversion dynamics of ultracold bosonic atoms to molecules in an external field with a Gaussian temporal shape and a linear frequency sweep. Under the mean-field theory, we study the atom–molecule conversion efficiency and the dynamics in the conversion process. By using the Fock-state basis, we further research the quantum many-body dynamics, wherein the many-body effect on the conversion is discussed. We find that the atom–molecule conversion dynamics depend on the particle interaction, peak coupled strength, sweep rate, and total particle number. Notably, some analytical results are derived in the regime without particle interactions and in the sudden limit, respectively. Our theory indicates that the ultracold atom–molecule conversion can be achieved stably and efficiently in the Gaussian external field model.We investigate the conversion dynamics of ultracold bosonic atoms to molecules in an external field with a Gaussian temporal shape and a linear frequency sweep. Under the mean-field theory, we study the atom–molecule conversion efficiency and the dynamics in the conversion process. By using the Fock-state basis, we further research the quantum many-body dynamics, wherein the many-body effect on the conversion is discussed. We find that the atom–molecule conversion dynamics depend on the particle interaction, peak coupled strength, sweep rate, and total particle number. Notably, some analytical results are derived in the regime without particle interactions and in the sudden limit, respectively. Our theory indicates that the ultracold atom–molecule conversion can be achieved stably and efficiently in the Gaussian external field model.

Journal of the Optical Society of America BAug 30, 20192 citations

Control of the dynamics of coupled atomic-molecular Bose-Einstein condensates: Modified Gross-Pitaevskii approach

Moumita Gupta, Krishna Rai Dastidar

We study the dynamics of the atomic and molecular Bose-Einstein condensates (BECs) of $^{87}\text{R}\text{b}$ in a spherically symmetric trap coupled by stimulated Raman photoassociation process. Considering the higher order nonlinearity in the atom-atom interaction we analyze the dynamics of the system using coupled modified Gross-Pitaevskii (MGP) equations and compare it with mean-field coupled Gross-Pitaevskii (GP) dynamics. Considerable differences in the dynamics are obtained in these two approaches at large scattering length, i.e., for large values of peak-gas parameter ${x}_{pk}\ensuremath{\ge}{10}^{\ensuremath{-}3}$. We show how the dynamics of the coupled system is affected when the atom-molecule and molecule-molecule interactions are considered together with the atom-atom interaction and also when the strengths of these three interactions are increased. The effect of detuning on the efficiency of conversion of atomic fractions into molecules is demonstrated and the feasibility of maximum molecular BEC formation by varying the Raman detuning parameter at different values of time is explored. Thus by varying the Raman detuning and the scattering length for atom-atom interaction one can control the dynamics of the coupled atomic-molecular BEC system. We have also solved coupled Gross-Pitaevskii equations for atomic to molecular condensate formation through magnetic Feshbach resonance in a BEC of $^{85}\text{R}\text{b}$ . We found similar features for oscillations between atomic and molecular condensates noted in previous theoretical study and obtained fairly good agreement with the evolution of total atomic condensate observed experimentally.We study the dynamics of the atomic and molecular Bose-Einstein condensates (BECs) of $^{87}\text{R}\text{b}$ in a spherically symmetric trap coupled by stimulated Raman photoassociation process. Considering the higher order nonlinearity in the atom-atom interaction we analyze the dynamics of the system using coupled modified Gross-Pitaevskii (MGP) equations and compare it with mean-field coupled Gross-Pitaevskii (GP) dynamics. Considerable differences in the dynamics are obtained in these two approaches at large scattering length, i.e., for large values of peak-gas parameter ${x}_{pk}\ensuremath{\ge}{10}^{\ensuremath{-}3}$. We show how the dynamics of the coupled system is affected when the atom-molecule and molecule-molecule interactions are considered together with the atom-atom interaction and also when the strengths of these three interactions are increased. The effect of detuning on the efficiency of conversion of atomic fractions into molecules is demonstrated and the feasibility of maximum molecular BEC formation by varying the Raman detuning parameter at different values of time is explored. Thus by varying the Raman detuning and the scattering length for atom-atom interaction one can control the dynamics of the coupled atomic-molecular BEC system. We have also solved coupled Gross-Pitaevskii equations for atomic to molecular condensate formation through magnetic Feshbach resonance in a BEC of $^{85}\text{R}\text{b}$. We found similar features for oscillations between atomic and molecular condensates noted in previous theoretical study and obtained fairly good agreement with the evolution of total atomic condensate observed experimentally.

Physical Review AOct 20, 200913 citations

Controlling atom-field dynamics

Sergey V. Prants

Journal of Russian Laser ResearchJan 1, 19952 citations

We study the dynamics of the atomic and molecular Bose-Einstein condensates (BECs) of

^{87}\text{R}\text{b}

in a spherically symmetric trap coupled by stimulated Raman photoassociation process. Considering the higher order nonlinearity in the atom-atom interaction we analyze the dynamics of the system using coupled modified Gross-Pitaevskii (MGP) equations and compare it with mean-field coupled Gross-Pitaevskii (GP) dynamics. Considerable differences in the dynamics are obtained in these two approaches at large scattering length, i.e., for large values of peak-gas parameter ${x}_{pk}\ensuremath{\ge}{10}^{\ensuremath{-}3}$. We show how the dynamics of the coupled system is affected when the atom-molecule and molecule-molecule interactions are considered together with the atom-atom interaction and also when the strengths of these three interactions are increased. The effect of detuning on the efficiency of conversion of atomic fractions into molecules is demonstrated and the feasibility of maximum molecular BEC formation by varying the Raman detuning parameter at different values of time is explored. Thus by varying the Raman detuning and the scattering length for atom-atom interaction one can control the dynamics of the coupled atomic-molecular BEC system. We have also solved coupled Gross-Pitaevskii equations for atomic to molecular condensate formation through magnetic Feshbach resonance in a BEC of

^{85}\text{R}\text{b}

. We found similar features for oscillations between atomic and molecular condensates noted in previous theoretical study and obtained fairly good agreement with the evolution of total atomic condensate observed experimentally.