Kazimierz Rzcażewski

arXiv2009

Free expansion of a Bose-Einstein condensate at the presence of a thermal cloud

We investigate numerically the free-fall expansion of a $^{87}$Rb atoms condensate at nonzero temperatures. The classical field approximation is used to separate the condensate and the thermal cloud during the expansion. We calculate the radial and axial widths of the expanding condensate and find clear evidence that the thermal component changes the dynamics of the condensate. Our results are confronted against the experimental data.

cond-mat.quant-gas↗

arXiv2005

Thermally induced instability of a doubly quantized vortex in a Bose-Einstein condensate

We study the instability of a doubly quantized vortex topologically imprinted on $^{23}$Na condensate, as reported in recent experiment [Phys. Rev. Lett. \textbf{93}, 160406 (2004)]. We have performed numerical simulations using three-dimensional Gross-Pitaevskii equation with classical thermal noise. Splitting of a doubly quantized vortex turns out to be a process that is very sensitive to the presence of thermal atoms. We observe that even ve ry small thermal fluctuations, corresponding to 10 to 15% of thermal atoms, ca use the decay of doubly quantized vortex into two singly quantized vortices in tens of milliseconds. As in the experiment, the lifetime of doubly quantized vortex i s a monotonic function of the interaction strength.

cond-mat.other↗