Quantum Fluids Research

9807761帕卡德：这是一个低温物理项目，主要研究流经100纳米孔径阵列的超流体的性质。这项工作是基于最近的一项发现，即这样的阵列表现为约瑟夫森弱链接。该项目的一个主要部分将研究与此类阵列中的各种约瑟夫森效应相关的物理问题。实验将：(1)绘制电流-相位关系图作为温度和环境压力的函数；(2)确定非零量子相位差亚稳态的稳定性；(3)确定非零量子相位差亚稳态的稳定性；(4)寻找类似于超导Shapiro效应的混相效应；(5)确定存在非零压头的耗散机制；(6)确定磁通捕获和孔径阵列内部和附近的织构结构的影响。该项目的第二部分将侧重于探测He-4通过亚微米口径时与相位滑移有关的声辐射。将开发检测声辐射的技术。随后，将对声谱进行研究，以了解涡核形成的机制和约瑟夫森频率关系。该项目为研究生提供了很好的基础物理和实验物理培训。%这是一个低温物理项目，重点是了解超流体通过非常小的孔洞的动态行为。在超流体He-3的情况下，小于1/1000万米的孔径形成了所谓的量子弱链。当超流体被强迫通过如此小的孔洞时，流体不像普通液体那样向一个方向流动，而是以与液体所受力成正比的频率来回涌动。这些约瑟夫森振荡表明了流体电流与量子力学相位差之间的正弦关系。计划中的研究将扩大我们对这种关系后果的理解。在超流体He-4的情况下，理论认为通过孔洞的压力驱动的流动应该伴随着所谓约瑟夫森频率的声音信号。声谱将反映孔径内涡核的细节。声谱与外加压头之间的关系可能导致量子力学压力标准。该项目为研究生提供了很好的基础物理和实验物理培训。***

9807761 Packard This is low temperature physics project focusing on the properties of superfluid flowing through arrays of 100nm apertures. The work is based on the recent finding that such an array behaves as a Josephson weak link. A main part of the project will investigate the physics associated with the various Josephson effects in such arrays. The experiments will: (1) Map out the current-phase relation as a function of temperature and ambient pressure, (2) Determine the stability of metastable states of non-zero quantum phase difference, (3) Determine the stability of metastable state of non-zero quantum phase difference, (4) Look for phase mixing effects analogous to the superconducting Shapiro effect, (5) Determine the dissipative mechanism which exist a non-zero pressure head, and (6) Determine the effect of flux trapping and textural structures within and near the aperture array. The second part of the project will focus on detecting acoustic radiation associated with the phase slippage when He-4 passes through a submicron size aperture. Techniques to detect the acoustic radiation will be developed. Subsequently, the acoustic spectrum will be studied to learn about vortex nucleation mechanisms and the Josephson frequency relation. The project provides excellent training for graduate students in both fundamental and experimental physics. %%% This is a low temperature physics project that focuses on understanding the dynamic behavior of superfluids that pass through very small apertures. In the case of superfluid He-3, an aperture smaller than 1/10,000,000 meter forms a so-called quantum weak link. When the superfluid is forced through such a small aperture, instead of flowing in one direction like an ordinary liquid, the fluid surges back and forth at a frequency proportional to the force on the liquid. These Josephson oscillations indicate a sine-like relation ship between fluid current and quantum mechanical phase difference. The planned research will expand our understanding of the consequences of this relation. In the case of superfluid He-4, theory suggests that pressure driven flow through an aperture should be accompanied by a sound signal at the so-called Josephson frequency. The sound spectrum will reflect the detail of vortex nucleation within the aperture. The relation between the sound spectrum and the applied pressure head may lead to a quantum mechanical pressure standard. The project provides excellent training for graduate students in both fundamental and experimental physics. ***