Dynamics of Bose-Einstein Condensation in Higher Bands

Joseph V. Pulé

Lu Tie, Ju-Kui Xue

The nonlinear Landau—Zener tunneling and nonlinear Rabi oscillations of Bose—Einstein condensate (BEC) with higher-order atomic interaction between the Bloch bands in an accelerating optical lattice are discussed. Within the two-level model, the tunneling probability of BEC with higher-order atomic interaction between Bloch bands is obtained. We finds that the tunneling rate is closely related to the higher-order atomic interaction. Furthermore, the nonlinear Rabi oscillations of BEC with higher-order atomic interaction between the bands are discussed by imposing a periodic modulation on the level bias. Analytical expressions of the critical higher-order atomic interaction for suppressing/enhancing the Rabi oscillations are obtained. It is shown that the critical value strongly depends on the modulation parameters (i.e., the modulation amplitude and frequency) and the strength of periodic potential.

Wu‐Ming Liu

Vaibhav Sharma, Sayan Choudhury, Erich J. Mueller

Motivated by recent experiments, we explore the kinetics of Bose-Einstein condensation in the upper band of a double-well optical lattice. These experiments engineer a nonequilibrium situation in which the highest energy state in the band is macroscopically occupied. The system subsequently relaxes and the condensate moves to the lowest energy state. We model this process, finding that the kinetics occurs in three phases: The condensate first evaporates, forming a highly nonequilibrium gas with no phase coherence; energy is then redistributed among the noncondensed atoms; finally, the atoms recondense. We calculate the timescales for each of these phases and explain how this scenario can be verified through future experiments.

Benjamin Schlein

Liang Zhao-Xin, Hu Ban-Bi

Landau and dynamical instabilities of a Bose–Einstein condensate (BEC) in the excited bands of a one-dimensional optical lattice are investigated by the Gross–Pitaevskii theory. Our results show that there always exists Landau instability for a BEC in the whole region of excited bands. We also map out the dangerous zones of the dynamical instability. The experimental implications of the stability diagram are discussed.