Nonlinear Dependence Observed in Quadrupolar Collective Excitation of a Trapped BEC

Abstract

We report the experimental observation of the collective excitations induced in a magnetically trapped 87 Rb Bose-Einstein condensate. Low-lying mode excitations were studied by tracking the condensate's center-of-mass displacement, and its aspect ratio as a function of the hold time in the trap. We were able to partially control the modes onset by modulating the amplitude of the additional field gradient used to excite the BEC. The measured excitation frequencies were found to be in good agreement with the literature. We have also found that the modulation amplitude was able to change the phase of the center-of-mass oscillation. Finally, an interesting, non-linear dependence was observed on the condensate aspect ratio as a function of the perturbing amplitude which induces the quadrupolar mode.

Quantum turbulence in trapped atomic Bose–Einstein condensates

“…33). They found that this oscillation has the same frequency as it was found for the quadrupolar mode [209]. Furthermore, the behavior of the amplitude and the frequency of this oscillation, when the excitation amplitude A exc is increased, is the same as the one obtained for the quadrupolar mode [209].…”

“…In contrast to the previous data, where the hold time t hold was fixed, in Ref. [209] the momentum distribution was studied during different hold times, as seen in Fig. 33.…”

Investigations on momentum distributions and disorder in strongly out-of-equilibrium trapped Bose gases

“…In previous works, the transverse momentum distribution of excited Bose gases was used to reconstruct the 3D momentum distribution ( ) using the inverse Abel transform (47) and to study the coupling with collective modes. (49)(50) Here, the same idea is applied, but our procedure allow us to explore not only the azimuthally averaged cloud, but also its angular sections, allowing us to analyze the anisotropy of˜ ( ).…”

“…In this thesis, we study three ways to quantify the non-equilibrium regimes produced by the action of a oscillatory excitation in Bose gases, with the same excitation protocol that was used in previous works. (39,(46)(47)(48)(49)(50) We focus on studies of momentum distribution, powerspectrum of fluctuations, and continuous entropy to probe non-equilibrium regimes in cigarshaped trapped gases in the searching of turbulence. The apparatus for performing these experiments prepares an ultracold quantum gas of some nano-Kelvins in a magnetic trap and applies a well controlled oscillatory magnetic excitation.…”

Thermodynamics of a Bose gas: Sound velocity from global variables and equivalence with other approaches

“…During this project, we have worked in understanding the effects of this perturbations, mainly in the transition from a non perturbed state to an state were evidences of turbulence is found. The main studies were published in references (33,(43)(44) and other are submitted or in preparation. Also, in search for new methods to produce turbulence, we have successfully implemented the technique of topological phase imprinting (45)(46) to produce multicharged vortices.…”