Signature of Critical Point in Momentum Profile of Trapped Ultracold Bose Gases**Supported by the National Natural Science Foundation of China under Grant No 11104322, and the National Key Basic Research and Development Program of China under Grant No 2011CB921503.

Abstract

We present a new method to identify the critical point for the Bose-Einstein condensation (BEC) of a trapped Bose gas. We calculate the momentum distribution of an interacting Bose gas near the critical temperature, and find that it deviates significantly from the Gaussian profile as the temperature approaches the critical point. More importantly, the standard deviation between the calculated momentum spectrum and the Gaussian profile at the same temperature shows a turning point at the critical point, which can be used to determine the critical temperature. These predictions are also confirmed by our BEC experiment for magnetically trapped 87Rb gases.