School of Physical and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom.
J Phys Condens Matter. 2023 Jan 24;35(8). doi: 10.1088/1361-648X/acaba3.
We review fundamental problems involved in liquid theory including both classical and quantum liquids. Understanding classical liquids involves exploring details of their microscopic dynamics and its consequences. Here, we apply the same general idea to quantum liquids. We discuss momentum condensation in liquid helium which is consistent with microscopic dynamics in liquids and high mobility of liquid atoms. We propose that mobile transit atoms accumulate in the finite-energy state where the transit speed is close to the speed of sound. In this state, the transit energy is close to the oscillatory zero-point energy. In momentum space, the accumulation operates on a sphere with the radius set by interatomic spacing and corresponds to zero net momentum. We show that this picture is supported by experiments, including the measured kinetic energy of helium atoms below the superfluid transition and sharp peaks of scattered intensity at predicted energy. We discuss the implications of this picture including the macroscopic wave function and superfluidity.
我们回顾了包括经典液体和量子液体在内的液体理论所涉及的基本问题。理解经典液体涉及到探索其微观动力学及其后果的细节。在这里，我们将同样的一般思路应用于量子液体。我们讨论了液氦中的动量凝聚，这与液体中的微观动力学和液体原子的高迁移率是一致的。我们提出，迁移过渡原子在有限能量状态下积累，其中迁移速度接近声速。在这个状态下，迁移能量接近于振动的零点能。在动量空间中，积累发生在一个由原子间距离确定半径的球体上，对应于零净动量。我们表明，这一图像得到了实验的支持，包括测量低于超流转变的氦原子的动能和预测能量处散射强度的尖锐峰值。我们讨论了这一图像的含义，包括宏观波函数和超流性。
