Mass transport through solid helium

固体氦的质量传递

• 批准号: 1707340
• 负责人: Moses Chan
• 金额: $ 46.78万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-07-15 至 2022-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1707340&HistoricalAwards=false
• 关键词: Mass; transport; through; solid; helium

Non-technical abstractLiquid helium changes from a normal liquid to a superfluid at low temperatures. It is called a superfluid because it can flow with zero viscosity with no loss in energy. Once set flowing in a continuous channel, superfluid will never stop. This fascinating property is related to the fact that liquid helium enters a quantum state below 2.176 degrees Kelvin. Remarkably, recent experiments at the University of Massachusetts and Penn State found helium atoms can flow through solid helium samples like a superfluid. The Penn State team is measuring the flow rate of the helium atoms through solid helium samples of different densities, thicknesses, crystal orientations to understand the exact mechanism responsible for this phenomenon. The proposed experiments provide opportunities for postdocs, graduate and undergraduate students to receive the most rigorous trainings to be future scientists. The principal investigator and his students and post-docs are active participants in the full range of outreach activities sponsored by the Penn State Materials Research Science and Engineering Center (MRSEC) for K-12 students. These organized and coordinated outreach activities are far more effective than isolated individual efforts.Technical AbstractThe solid helium samples are sandwiched between superfluid leads in the form of porous Vycor glass cylinders infused with superfluid helium. The mass flow is thought to be related to the motion of edge dislocations and/or the transport of helium atoms through the superfluid screw dislocations in solid helium samples. Mass flow experiments through the superfluid/solid helium/superfluid "sandwiches' are in progress to test the veracity of the dislocation line model. Since dislocation lines are absent in solid helium grown inside highly porous silica aerogel, measurements in such solid samples provide a direct test on the necessity of dislocation lines for the phenomenon. Solid samples of different thicknesses ranging from 8 µm (where dislocation lines do not form a connected network) to a few mm are being studied to understand the effect of connectivity of the dislocation network. The dependence of crystal orientation is studied by affixing graphite crystals with their c-axis (which nucleates epitaxial growth of solid helium crystals) pointing either along or perpendicular to mass flow direction inside of the sample space. The mass flow through solid helium is driven by superfluid fountain pressure imposed across the samples. The flow rate as a function of temperature and the fountain pressure are measured to search for the boundary separating the dissipation-free and dissipative regions.

液氦在低温下从普通液体变成超流体。它被称为超流体，因为它可以在没有能量损失的情况下以零粘度流动。一旦在连续的通道中流动，超流体就永远不会停止。这个迷人的性质与液氦在2.176开氏度以下进入量子态的事实有关。值得注意的是，马萨诸塞州大学和宾夕法尼亚州立大学最近的实验发现，氦原子可以像超流体一样流过固体氦样品。宾夕法尼亚州立大学的研究小组正在通过不同密度、厚度、晶体取向的固体氦样品测量氦原子的流速，以了解造成这种现象的确切机制。拟议的实验为博士后，研究生和本科生提供了机会，接受最严格的培训，成为未来的科学家。主要研究者和他的学生和博士后都积极参与宾夕法尼亚州立大学材料研究科学与工程中心（MRSEC）为K-12学生赞助的全方位外联活动。这些有组织和协调的外展活动远比孤立的个人努力更有效。技术摘要固体氦样品夹在超流铅之间，这种超流铅是以注入超流氦的多孔Vycor玻璃柱的形式存在的。质量流被认为与固体氦样品中刃位错的运动和/或氦原子通过超流螺旋位错的输运有关。通过超流/固体氦/超流“三明治”的质量流实验正在进行中，以测试位错线模型的准确性。由于在高度多孔的二氧化硅气凝胶内生长的固体氦中不存在位错线，因此在这种固体样品中的测量提供了对位错线对于该现象的必要性的直接测试。正在研究不同厚度的固体样品，从8微米（其中位错线不形成连通网络）到几毫米，以了解位错网络连通性的影响。晶体取向的依赖性的研究通过附着石墨晶体与它们的c轴（成核固体氦晶体的外延生长）指向或者沿着或垂直于样品空间内的质量流方向。通过固体氦的质量流由施加在样品上的超流体喷泉压力驱动。测量作为温度和喷泉压力的函数的流率，以寻找分离无耗散区和耗散区的边界。

项目成果

Tuning the Chern number in quantum anomalous Hall insulators

• DOI: 10.1038/s41586-020-3020-3
• 发表时间: 2020-12
• 期刊: Nature
• 影响因子: 64.8
• 作者: Yi-Fan Zhao;Ruoxi Zhang;Ruobing Mei;Ling Zhou;H. Yi;Ya-Qi Zhang;Jiabin Yu;Run Xiao;Ke Wan

Mass transport through dislocation network in solid He4

固体 He4 中通过位错网络的质量传输

• DOI: 10.1103/physrevb.99.140502
• 发表时间: 2019
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Shin, Jaeho;Chan, Moses H.
• 通讯作者: Chan, Moses H.

Recent Experimental Studies on Solid 4He

固体 4He 的最新实验研究

• DOI: 10.1007/s10909-021-02636-1
• 发表时间: 2021
• 期刊: Journal of Low Temperature Physics
• 影响因子: 2
• 作者: Chan, Moses H.

Long-range superconducting proximity effect in nickel nanowires

• DOI: 10.1103/physrevresearch.4.023133
• 发表时间: 2021-07
• 期刊: Physical Review Research
• 影响因子: 4.2
• 作者: Jue Jiang;Weiwei Zhao;Fei Wang;R. Du;L. Miao;Ke Wang;Qi Li;Cui-Zu Chang;M. Chan

Realization of the Axion Insulator State in Quantum Anomalous Hall Sandwich Heterostructures

• DOI: 10.1103/physrevlett.120.056801
• 发表时间: 2018-01-31
• 期刊: PHYSICAL REVIEW LETTERS
• 影响因子: 8.6
• 作者: Xiao, Di;Jiang, Jue;Chang, Cui-Zu
• 通讯作者: Chang, Cui-Zu