Quantum Fluids Research

小行星9807761 这 是低温物理项目， 超流体流过阵列的性质 的 100 nm孔径。这项工作是基于最近的发现，这样的阵列的行为作为约瑟夫森弱链接。该项目的一个主要部分将研究与这种阵列中的各种约瑟夫森效应相关的物理学。这些实验将：（1）绘制出作为温度和环境压力的函数的电流-相位关系;（2）确定非零量子相位差的亚稳态的稳定性;（3）确定 的 非零量子亚稳态 （4）寻找类似超导Shapiro效应的相位混合效应，（5）确定存在非零压头的耗散机制，（6）确定孔阵列内和附近的磁通捕获和织构结构的影响。该项目的第二部分将侧重于检测当He-4通过亚微米尺寸孔径时与相位滑移相关的声辐射。 将开发探测声辐射的技术。 随后，将研究声谱以了解涡旋成核机制和约瑟夫森频率关系。 该项目为基础物理和实验物理的研究生提供了良好的培训。 这是一个低温物理项目，重点是了解通过非常小的孔径的超流体的动态行为。在超流He-3的情况下，小于1/10，000，000米的孔径形成了所谓的量子弱链接。当超流体被迫通过这样一个小孔时，它并不像普通液体那样朝一个方向流动，而是以与力成比例的频率来回涌动 在液体上。 这些 约瑟夫森振荡表明流体电流和量子力学相位差之间存在类似正弦的关系。 计划中的研究将扩大我们对这种关系的后果的理解。 在超流体He-4的情况下，理论表明， 通过孔的压力驱动流应该 伴随着一个声音信号在所谓的 约瑟夫森频率声谱将反映孔内涡流成核的细节。声谱和所施加的压头之间的关系可能导致量子力学压力标准。该项目提供出色的培训 为 研究生在两个 基本 和实验物理学 ***

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. ***