Hodby E, Maragò O M, Hechenblaikner G, Foot C J
Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom.
Phys Rev Lett. 2001 Mar 12;86(11):2196-9. doi: 10.1103/PhysRevLett.86.2196.
We report the first experimental observation of Beliaev coupling between collective excitations of a Bose-Einstein condensed gas. Beliaev coupling is not predicted by the Gross-Pitaevskii equation and so this experiment tests condensate theory beyond the mean field approximation. Measurements of the amplitude of a high frequency scissors mode show that the Beliaev process transfers energy to a lower-lying mode and then back and forth between these modes, unlike Landau processes which lead to a monotonic decrease in amplitude. To enhance the Beliaev process we adjusted the geometry of the magnetic trapping potential to give a frequency ratio of 2 to 1 between the two scissors modes.
我们报告了玻色 - 爱因斯坦凝聚气体集体激发之间贝利耶夫耦合的首次实验观测结果。格罗斯 - 皮塔耶夫斯基方程并未预测到贝利耶夫耦合，因此该实验对超出平均场近似的凝聚体理论进行了检验。对高频剪刀模式振幅的测量表明，与导致振幅单调减小的朗道过程不同，贝利耶夫过程将能量转移到较低能级模式，然后在这些模式之间来回转移。为了增强贝利耶夫过程，我们调整了磁阱势的几何形状，使两种剪刀模式之间的频率比为2比1。
