Quantum kinetic theory. VI. The growth of a Bose-Einstein condensate - art. no. 033606

A detailed analysis of the growth of a Bose-Einstein condensate is given, b ased on quantum kinetic theory, in which we take account of the evolution o f the occupations of lower trap levels, and of the full Bose-Einstein formu la for the occupations of higher trap levels, as well as the Bose-stimulate d direct transfer of atoms to the condensate level introduced by Gardiner e t nl. [Phys. Rev. Lett. 79, 1793 (1997); 81, 5266 (1998)]. We find good agr eement with experiment at higher temperatures, but at lower temperatures th e experimentally observed growth rate is somewhat more rapid. We also confi rm the picture of the "kinetic" region of evolution, introduced by Kagan, S vistunov, and Shlyapnikov (Zh. Eksp. Teor. Fit. 101, 538 (1992) [Sov. Phys. JETP 75, 387 (1992)]), for the time up to the initiation of the condensate . The behavior after initiation essentially follows our original growth equ ation, but with a substantially increased rate coefficient. Our modeling of growth implicitly gives a model of the spatial shape of the density profil e of the condensate-vapor system as the condensate grows, and thus provides an alternative to the present phenomenological fitting procedure, based on the sum of a zero-chemical potential vapor and a Thomas-Fermi-shaped conde nsate. Our method fives substantially different results for condensate numb ers and temperatures obtained from phenomenological fits, but fits the publ ished column density data very well.