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Kinetic Theory of Collective Excitations and Damping in Bose-Einstein Condensed Gases

U. Al Khawaja·H. T. C. Stoof
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Abstract

We calculate the frequencies and damping rates of the low-lying collective modes of a Bose-Einstein condensed gas at nonzero temperature. We use a complex nonlinear Schrödinger equation to determine the dynamics of the condensate atoms, and couple it to a Boltzmann equation for the noncondensate atoms. In this manner we take into account both collisions between noncondensate-noncondensate and condensate-noncondensate atoms. We solve the linear response of these equations, using a time-dependent gaussian trial function for the condensate wave function and a truncated power expansion for the deviation function of the thermal cloud. As a result, our calculation turns out to be characterized by two dimensionless parameters proportional to the noncondensate-noncondensate and condensate-noncondensate mean collision times. We find in general quite good agreement with experiment, both for the frequencies and damping of the collective modes.

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U. Al Khawaja, H. T. C. Stoof. 2000-03-31. Kinetic Theory of Collective Excitations and Damping in Bose-Einstein Condensed Gases. https://doi.org/10.1103/physreva.62.053602

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