Sykes Andrew G, Davis Matthew J, Roberts David C
The University of Queensland, School of Mathematics and Physics, ARC Centre of Excellence for Quantum-Atom Optics, Brisbane 4072, Australia.
Phys Rev Lett. 2009 Aug 21;103(8):085302. doi: 10.1103/PhysRevLett.103.085302. Epub 2009 Aug 18.
The existence of frictionless flow below a critical velocity for obstacles moving in a superfluid is well established in the context of the mean-field Gross-Pitaevskii theory. We calculate the next order correction due to quantum and thermal fluctuations and find a nonzero force acting on a delta-function impurity moving through a quasi-one-dimensional Bose-Einstein condensate at all subcritical velocities and at all temperatures. The force occurs due to an imbalance in the Doppler shifts of reflected quantum fluctuations from either side of the impurity. Our calculation is based on a consistent extension of Bogoliubov theory to second order in the interaction strength, and finds new analytical solutions to the Bogoliubov-de Gennes equations for a gray soliton. Our results raise questions regarding the quantum dynamics in the formation of persistent currents in superfluids.
在平均场戈斯-皮塔耶夫斯基理论的背景下，对于在超流体中移动的障碍物，低于临界速度时无摩擦流动的存在已得到充分证实。我们计算了由于量子和热涨落引起的下一阶修正，并发现对于在所有亚临界速度和所有温度下通过准一维玻色-爱因斯坦凝聚体移动的δ函数杂质，存在一个非零力。该力是由于杂质两侧反射的量子涨落的多普勒频移不平衡而产生的。我们的计算基于将博戈留波夫理论一致地扩展到相互作用强度的二阶，并找到了灰色孤子的博戈留波夫-德热纳方程的新解析解。我们的结果引发了关于超流体中持续电流形成中的量子动力学的问题。
