arXiv 1207.34402012-07-27cond-mat.quant-gas

玻色-爱因斯坦凝聚体的声子色散关系

The phonon dispersion relation of a Bose-Einstein condensate

I. Shammass, S. Rinott, A. Berkovitz, R. Schley, J. Steinhauer

备注：: contains additional simulations and analysis which show a 3D to 1D transition
发表信息：: Phys. Rev. Lett. 109, 195301 (2012)
DOI：: 10.1103/PhysRevLett.109.195301

摘要：

我们测量了玻色-爱因斯坦凝聚体中声子驻波的振荡，从而得到色散关系。我们提出了短布拉格脉冲技术，它激发的驻波。随后的振荡在原位观察。可以看出，声子经历了3D到1D的转变，当它们的波长变得比凝聚体的横向半径长。一维区域在色散关系中包含一个拐点，根据朗道判据，该拐点会降低超流临界速度。拐点也表示群速度的最小值，尽管最小值不足以导致旋转。3D-1D的过渡也导致驻波振荡的寿命增加，局部密度近似的崩溃。此外，静态结构因子的测量在长波长制度。新技术的高灵敏度使测量成为可能。

英文摘要：

We measure the oscillations of a standing wave of phonons in a Bose-Einstein condensate, thus obtaining the dispersion relation. We present the technique of short Bragg pulses, which stimulates the standing wave. The subsequent oscillations are observed in situ. It is seen that the phonons undergo a 3D to 1D transition, when their wavelength becomes longer than the transverse radius of the condensate. The 1D regime contains an inflection point in the dispersion relation, which should decrease the superfluid critical velocity according to the Landau criterion. The inflection point also represents a minimum in the group velocity, although the minimum is not deep enough to result in a roton. The 3D-1D transition also results in an increase in the lifetime of the standing-wave oscillations, and a breakdown of the local density approximation. In addition, the static structure factor is measured in the long-wavelength regime. The measurements are enabled by the high sensitivity of the new technique.

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英文摘要：

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