Coherent Diffraction Imaging with Superfluid He Nano-Droplets

液氦中的超流性一个世纪以来一直吸引着凝聚态物理学家，直到今天仍然是一个非常感兴趣的话题。这一行为是宏观量子效应的一个例子，类似于某些材料中发生的超导行为。在液氦中，这种宏观量子行为以许多令人着迷的方式表现出来，其中之一是正常液体所表现出的粘度的消失。这导致了许多有趣的现象，如长寿命量子涡旋线的出现。该项目将利用在直线加速器相干光源上新开发的x射线自由电子激光器来探索高度悬浮的氦液滴的流体动力学。这项研究将产生的新见解将有助于我们理解涡旋对从超导体到中子星的各种系统的影响。此外，在该项目期间开发的工具将对材料科学家开发新的纳米材料大有裨益。技术摘要该项目将探索4-He液滴中的量子旋转，为介观尺度的量子流体动力学带来新的物理见解。具体地说，这项研究将有助于描述在可用角动量-角速度相空间中旋转的量子液滴，并确定旋转超流和经典液滴是否属于相同的形状家族；(Ii)提供液滴中固定的形状和涡旋(N=1-200)，这些仍然没有实验或理论上的研究；(Iii)通过研究带有Xe团簇的涡旋来揭示涡旋质量对其动力学的影响；以及(Iv)阐明极端涡度下的量子旋转，比整体实验中获得的高出约100000倍，提供了进入量子液体中未探索的旋转激发区域的途径。在直线加速器相干光源自由电子激光器上的单发飞秒X射线相干衍射成像将与新的图像重建算法相结合，用于重建液滴形状和液滴内涡旋位置的真实空间图像。

Non-technical AbstractSuperfluidity in liquid helium has fascinated condensed matter physicists for a century and remains a topic of great interest even today. This behavior is an example of a macroscopic quantum effect similar to the superconducting behavior that occurs in some materials. In liquid helium this macroscopic quantum behavior manifests itself in many fascinating ways one of which is the disappearance of the viscosity exhibited by normal liquids. This leads to many interesting phenomena such as the appearance of long lived quantum vortex lines. This project will make use of the newly developed x-ray free electron laser at the Linac Coherent Light Source to explore the hydrodynamics of feely suspended helium droplets. The new insights this research will produce will help in our understanding of the effects of vortices on systems ranging from superconductors to neutron stars. In addition, the tools that will be developed during this project will be of great benefit to materials scientists developing new nanomaterials.Technical AbstractThis project will explore quantum rotation in 4-He droplets to bring new physical insights into quantum hydrodynamics at the meso-scale. In particular, this study will: (i) contribute to the description of rotating quantum droplets across the available angular momentum - angular velocity phase space and determine if the rotating superfluid and classical droplets belong to the same families of shapes; (ii) provide stationary shapes and configurations of vortices (N = 1-200) in a droplet, which remain unstudied experimentally or theoretically; (iii) reveal the effect of vortex mass on their dynamics by studying vortices decorated with Xe clusters; and (iv) elucidate quantum rotation at extreme vorticity, up to a factor of about 100000 higher than attained in bulk experiments, providing access to unexplored regimes of rotational excitation in quantum liquids. Single-shot femtosecond X-ray coherent diffractive imaging at the Linac Coherent Light Source free electron laser coupled with new image reconstruction algorithms will be used to reconstruct real space images of the shape of the droplets and the location of vortices within the droplet.