Phonon dispersion relation of an atomic Bose-Einstein condensate.
Phonon dispersion relation of an atomic Bose-Einstein condensate.
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原子玻色-爱因斯坦凝聚体的声子色散关系。
DOI：
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发表时间：
2012
影响因子：
8.6
通讯作者：
Jeff Steinhauer
中科院分区：
文献类型：
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作者：
I. Shammass;S. Rinott;A. Berkovitz;R. Schley;Jeff Steinhauer
我们测量了玻色-爱因斯坦凝聚体中声子自由演化驻波的时间振荡。我们提出了短布拉格脉冲的技术，它刺激驻波。随后的振荡在原位观察。振荡的频率给出色散关系，振幅给出静态结构因子，衰减给出退相时间。这项新技术的灵敏度比布拉格光谱法高出几个数量级，可以观察到与局部密度近似的偏差。具体地说，可以看出，声子经历了从三维到一维的过渡，当它们的波长变得比凝聚体的横向半径长。一维制度包含一个拐点的色散关系，超流临界速度的减少，最小的群速度，并增加驻波振荡的寿命。
We measure the time oscillations of a freely evolving standing wave of phonons in a Bose-Einstein condensate. We present the technique of short Bragg pulses, which stimulates the standing wave. The subsequent oscillations are observed in situ. The frequency of the oscillations gives the dispersion relation, the amplitude gives the static structure factor, and the decay gives the dephasing time. The new technique gives orders of magnitude more sensitivity than Bragg spectroscopy, allowing for the observation of deviations from the local density approximation. Specifically, it is seen that the phonons undergo a transition from three dimensions to one dimension, when their wavelength becomes longer than the transverse radius of the condensate. The one-dimensional regime contains an inflection point in the dispersion relation, a decrease in the superfluid critical velocity, a minimum in the group velocity, and an increase in the lifetime of the standing wave oscillations.