Nonlinear Self-Trapping of Matter Waves in Periodic Potentials

Abstract

We report the first experimental observation of nonlinear self-trapping of Bose-condensed 87 Rb atoms in a one dimensional waveguide with a superimposed deep periodic potential . The trapping effect is confirmed directly by imaging the atomic spatial distribution. Increasing the nonlinearity we move the system from the diffusive regime, characterized by an expansion of the condensate, to the nonlinearity dominated self-trapping regime, where the initial expansion stops and the width remains finite. The data are in quantitative agreement with the solutions of the corresponding discrete nonlinear equation. Our results reveal that the effect of nonlinear self-trapping is of local nature, and is closely related to the macroscopic self-trapping phenomenon already predicted for double-well systems.

Self-trapping of Bose-Einstein condensates in optical lattices

“…With such an analysis, we have confirmed the previous study [6] that the self-trapping observed in optical lattices is closely related to the selftrapping of a BEC in the double-well potential [7,8,10]. From this analysis, we have also explored a possible mechanism of the formation of steep edges.…”

“…The other frequency ω is so chosen that the initial rms-width of BEC wave packet is 7.6µm as in the experiments [6]. This width corresponds to about 100 wells occupied.…”

“…After a sufficiently long evolution time, the self-trapping breaks down and the wave packet starts to expand again as seen in Fig.2. Since the break-down time is much longer than the observation used in the current experiment [6], these results need to be verified in future experiments. This breakdown of self-trapping is likely caused by the leakage of atoms at the outmost wells, or as we shall call it the dripping effect.…”

“…The wave function ψ is normalized to one. In our numerical simulation, we use the following values from the experiment [6], λ = 2π/k L = 783nm, V 0 = 10E r , and ω ⊥ = 2π × 230Hz.…”

“…Another intriguing phenomenon, self-trapping, was recently observed experimentally in this system [6]. In this experiment, a BEC with repulsive interaction was first prepared in a dipole trap.…”