Anomalous effects in a trapped Bose-Einstein condensate

David A. W. Hutchinson, R. J. Dodd, Nick P. Proukakis +4 more

Sergey V. Tarasov, Vl. V. Kocharovsky, Vitaly V. Kocharovsky

We analytically calculate the statistics of Bose-Einstein condensate (BEC) fluctuations in an interacting gas trapped in a three-dimensional cubic or rectangular box with the Dirichlet, fused or periodic boundary conditions within the mean-field Bogoliubov and Thomas-Fermi approximations. We study a mesoscopic system of a finite number of trapped particles and its thermodynamic limit. We find that the BEC fluctuations, first, are anomalously large and non-Gaussian and, second, depend on the trap's form and boundary conditions. Remarkably, these effects persist with increasing interparticle interaction and even in the thermodynamic limit-only the mean BEC occupation, not BEC fluctuations, becomes independent on the trap's form and boundary conditions.

Abdelâali Boudjemâa

We study the properties of a Bose-Einstein-condensate (BEC)--impurity mixture at finite temperature employing the time-dependent Hartree-Fock Bogoliubov (TDHFB) theory which is a set of coupled nonlinear equations of motion for the condensate and its normal and anomalous fluctuations on the one hand and for impurity on the other. The numerical solutions of these equations in the static quasi-one-dimensional regime show that the thermal cloud and the anomalous density are deformed as happens to the condensate and the impurity becomes less localized at nonzero temperatures. Effects of the BEC fluctuations on the self-trapping state are studied in homogeneous weakly interacting BEC-impurity at low temperature. The self-trapping threshold is also determined in such a system. The formation of solitons in the BEC-impurity mixture at finite temperature is investigated.

Chen Ning Yang

Hongwei Xiong, Shujuan Liu, Guoxiang Huang

We investigate the particle-number fluctuations due to the collective excitations created in a two-dimensional (2D) and a quasi-2D Bose-Einstein condensates (BECs) at low temperature. We find that the fluctuations display an anomalous behavior, i.e., for the 2D BEC they are proportional to ${N}^{2},$ where N is the total number of particles. For the quasi-2D BEC, the particle-number fluctuations are proportional not only to ${N}^{2}$ but also to the square root of the trapping frequency in the strongly confined direction.

Yeong E. Kim, Alexander L. Zubarev