Abstract

The mean-field Gross-Pitaevskii equation with repulsive interactions exhibits frictionless flow when stirred by an obstacle below a critical velocity. Here we go beyond the mean-field approximation to examine the influence of quantum fluctuations on this threshold behaviour in a one-dimensional Bose gas in a ring. Using the truncated Wigner approximation, we perform simulations of ensembles of trajectories where the Bose gas is stirred with a repulsive obstacle below the mean-field critical velocity. We observe the probabilistic formation of grey solitons which subsequently decay, leading to an increase in the momentum of the fluid. The formation of the first soliton leads to a soliton cascade, such that the fluid rapidly accelerates to minimise the speed difference with the obstacle. We measure the initial rate of momentum transfer, and relate it to macroscopic tunnelling between quantised flow states in the ring.

Graphical abstract

中文翻译：

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量子涨落对一维玻色气体超流体临界速度的影响

摘要

具有排斥相互作用的平均场Gross-Pitaevskii方程在被低于临界速度的障碍物搅动时表现出无摩擦流动。在这里，我们超越了平均场近似，研究了环中一维玻色气体中量子涨落对该阈值行为的影响。使用截断的Wigner逼近，我们对轨迹集合进行了模拟，在该轨迹中，玻色气体与低于平均场临界速度的排斥性障碍一起搅拌。我们观察到了灰色孤子的概率形成，该概率随后衰变，导致流体动量增加。第一孤子的形成导致孤子级联，使得流体迅速加速以最小化与障碍物的速度差。我们测量动量传递的初始速率

图形概要