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 Na-23 condensate, as reported in recent experiment (Shin et al 2004 Phys. Rev. Lett. 93 160406). 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 very small thermal fluctuations, corresponding to 10-15% of thermal atoms, cause 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 is a monotonic function of the interaction strength.