Laboratoire Kastler Brossel, Collège de France, CNRS, ENS-PSL University, Sorbonne Université, 11 Place Marcelin Berthelot, 75005 Paris, France.
Phys Rev Lett. 2018 Oct 5;121(14):145301. doi: 10.1103/PhysRevLett.121.145301.
In superfluid systems several sound modes can be excited, such as, for example, first and second sound in liquid helium. Here, we excite running and standing waves in a uniform two-dimensional Bose gas and we characterize the propagation of sound in both the superfluid and normal regimes. In the superfluid phase, the measured speed of sound is in good agreement with the prediction of a two-fluid hydrodynamic model, and the weak damping is well explained by the scattering with thermal excitations. In the normal phase we observe a stronger damping, which we attribute to a departure from hydrodynamic behavior.
在超流体系中可以激发出多种声波模式，例如液氦中的第一类和第二类声。在这里，我们在均匀二维玻色气体中激发出传播波和驻波，并对在超导态和正常态下的声波传播进行了研究。在超导相中，测量得到的声速与双流体流体动力学模型的预测值吻合得很好，而与热激发的散射相关的微弱阻尼也得到了很好的解释。在正常相中，我们观察到了更强的阻尼，我们将其归因于对流体动力学行为的偏离。
