有限温度下运动光晶格中玻色气体的临界速度
Critical Velocity in a Bose Gas in a Moving Optical Lattice at Finite Temperatures
摘要：
研究了有限温度下运动一维光晶格势场中玻色凝聚气体的临界速度。求解Gross-Pitaeavskii方程和Bogoliubov方程，在Popov近似下，我们计算了不同晶格速度下的Bogoliubov激发。从负激发能的条件出发，确定了临界速度与晶格深度和温度的函数关系。我们发现临界速度随温度的升高而迅速降低，这一结果与实验观察相一致。此外，临界速度随着晶格深度的增加而迅速减小。这一趋势比以往忽略径向热激励效应的结果更为显著。
英文摘要：
We study the critical velocity of a Bose-condensed gas in a moving one-dimensional (1D) optical lattice potential at finite temperatures. Solving the Gross-Pitaeavskii equation and the Bogoliubov equations, within the Popov approximation, we calculate the Bogoliubov excitations with varying lattice velocity. From the condition of the negative excitation energy, we determine the critical velocity as a function of the lattice depth and the temperature. We find that the critical velocity decreases rapidly with increasing the temperature; this result is consistent with the experimental observations. Moreover, the critical velocity shows a rapid decrease with increasing lattice depth. This tendency is much more significant than in the previous works ignoring the effect of thermal excitations in the radial direction.
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