Superfluid 3He at UltraLow Temperatures

超低温下的超流体 3He

• 批准号: EP/L000016/1
• 负责人: Richard Haley
• 金额: $ 126.69万
• 依托单位: Lancaster University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2013
• 资助国家: 英国
• 起止时间: 2013 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FL000016%2F1
• 关键词: Superfluid; 3He; UltraLow; Temperatures

Superfluid 3He has many exotic properties and provides a model system for investigating fundamental processes. It is the only accessible material which has absolute purity. It supports dissipationless flow of mass, spin and orbital angular momentum which give rise to a variety of macroscopic coherence phenomena. The coherent orbital and spin properties are described by vector order parameters which vary on very large length scales, limited only by the size of the experimental cell. Our group specialises in novel cooling and measurement techniques at ultralow temperatures. We routinely cool superfluid 3He to record low temperatures where the few remaining thermal excitations are highly ballistic and the superfluid is essentially in its groundstate.We plan a series of experiments to study fundamental properties of phase transitions and interfaces. The A-B phase transition at low temperatures occurs at a fairly large magnetic field of order 0.4Tesla. Using custom made superconducting solenoids we can accurately control the magnetic field profile to stabilise and manipulate the A-B phase interface. We will incorporate techniques to measure very small, femtowatt, energy dissipations when the interface moves. We will oscillate the interface to investigate how the different dissipation mechanisms depend on the velocity amplitude and the frequency. At low velocity/frequency the interface dissipates energy by scattering thermal excitations. At higher velocities/frequencies dissipation may occur by generating new excitations via processes analogous to particle production in high energy physics. We also expect the motion to induce interesting dynamics of the orbital textures on both sides of the interface.The transition from A-phase to B-phase on cooling presents a long outstanding puzzle. According to standard theories the transition should not occur, even on astronomical timescales. Experiments show that the transition occurs quite readily. A possible explanation has been proposed based on `resonant tunneling' between metastable states. We will perform controlled experiments to test this. By forming a sharp magnetic field minimum we will shape the B-phase nucleating region into a bubble remote from the cell walls to eliminate surface mechanisms. According to the resonant tunneling model, the transition should only occur at particular temperatures and magnetic fields, giving a clear experimental signature.We will construct an aerogel-based 3He cooling stage to access lower temperatures. We will directly cool, by demagnetization, the nano-network of solid 3He layers which coat the aerogel strands. These layers are in extremely good thermal contact with the surrounding liquid owing to rapid exchange. The stage will have an enclosed cavity to enable experiments on bulk superfluid 3He. The cavity will be completely surrounded by cold demagnetised aerogel to eliminate heat leaks. We believe it is possible to reach a new temperature regime where there are only a few remaining thermal excitations in the entire volume. We will use Nuclear Magnetic Resonance to simultaneously probe the bulk superfluid, the aerogel-confined fluid and the nanometer solid 3He layers. This will enable us to explore new phenomena in the extreme low temperature limit. We will study ultralow temperature magnetic phase transitions in the solid layers. In the bulk B-phase we will investigate the Persistent Precessing Domain (PPD), a Bose-Einstein condensate of magnons. The free decay of the PPD may last several hours at the lowest temperatures. Under such extreme conditions, additional dissipation mechanisms may emerge, such as from ionisation tracks left by cosmic rays.The research will lead to a better understanding of fundamental processes in quantum systems, phase transitions and phase interfaces, as well extending the capabilities of cooling technology.

超流3 He具有许多奇异的性质，为研究基本过程提供了一个模型系统。它是唯一可获得的具有绝对纯度的材料。它支持质量、自旋和轨道角动量的无耗散流动，从而产生各种宏观相干现象。的相干轨道和自旋属性描述的矢量顺序参数变化的非常大的长度尺度上，仅限于实验细胞的大小。我们的团队专门研究超低温下的新型冷却和测量技术。我们定期冷却超流3 He以记录低温，其中少数剩余的热激发是高度弹道的，并且超流基本上处于基态。我们计划进行一系列实验来研究相变和界面的基本性质。低温下的A-B相变发生在0.4T量级的相当大的磁场中。使用定制的超导磁体，我们可以精确地控制磁场分布，以稳定和操纵A-B相界面。我们将结合技术来测量非常小的，毫微微瓦，能量耗散时，接口移动。我们将振荡界面，以研究不同的耗散机制如何依赖于速度振幅和频率。在低速度/频率下，界面通过散射热激发来耗散能量。在更高的速度/频率下，耗散可能通过经由类似于高能物理中的粒子产生的过程产生新的激发而发生。我们还期望这种运动能引起界面两侧的轨道织构的有趣的动力学变化。冷却时从A相到B相的转变是一个长期悬而未决的难题。根据标准理论，这种转变不应该发生，即使在天文时间尺度上也是如此。实验表明，这种转变很容易发生。根据亚稳态之间的“共振隧穿”提出了一种可能的解释。我们将进行受控实验来验证这一点。通过形成一个尖锐的磁场最小值，我们将形状的B相成核区成一个远离细胞壁的气泡，以消除表面机制。根据共振隧穿模型，这种转变应该只发生在特定的温度和磁场下，给出了明确的实验特征。我们将构建一个基于气凝胶的3 He冷却台，以获得更低的温度。我们将通过退磁直接冷却覆盖气凝胶股线的固体3 He层的纳米网络。由于快速交换，这些层与周围的液体具有极好的热接触。该阶段将有一个封闭的空腔，以使大量的超流体3 He的实验。空腔将完全被冷的退磁气凝胶包围，以消除热泄漏。我们相信，这是可能的，以达到一个新的温度制度，只有少数剩余的热激发在整个体积。我们将利用核磁共振同时探测大块超流体、气凝胶约束流体和纳米固体3 He层。这将使我们能够探索极端低温极限下的新现象。我们将研究固体层中的超低温磁相变。在体B相，我们将研究持续进动域（PPD），玻色爱因斯坦凝聚的磁振子。PPD的自由衰变在最低温度下可持续数小时。在这种极端条件下，可能会出现额外的耗散机制，例如宇宙射线留下的电离轨迹。这项研究将有助于更好地理解量子系统、相变和相界面的基本过程，并扩展冷却技术的能力。

项目成果

Transport of bound quasiparticle states in a two-dimensional boundary superfluid.

• DOI: 10.1038/s41467-023-42520-y
• 发表时间: 2023-11-02
• 期刊: NATURE COMMUNICATIONS
• 影响因子: 16.6
• 作者: Autti, Samuli;Haley, Richard P;Jennings, Asher;Pickett, George R;Poole, Malcolm;Schanen, Roch;Soldatov, Arkady A;Tsepelin, Viktor;Vonka, Jakub;Zavjalov, Vladislav V;Zmeev, Dmitry E
• 通讯作者: Zmeev, Dmitry E

Fundamental dissipation due to bound fermions in the zero-temperature limit.

• DOI: 10.1038/s41467-020-18499-1
• 发表时间: 2020-09-21
• 期刊: Nature communications
• 影响因子: 16.6
• 作者: Autti S;Ahlstrom SL;Haley RP;Jennings A;Pickett GR;Poole M;Schanen R;Soldatov AA;Tsepelin V;Vonka J;Wilcox T;Woods AJ;Zmeev DE
• 通讯作者: Zmeev DE

Thermal Transport in Nanoelectronic Devices Cooled by On-Chip Magnetic Refrigeration.

片上磁制冷冷却的纳米电子器件中的热传输。

• DOI: 10.1103/physrevlett.131.077001
• 发表时间: 2023
• 期刊: Physical review letters
• 影响因子: 8.6
• 作者: Autti S

Response of a Mechanical Oscillator in Solid 4He

固体 4He 中机械振荡器的响应

• DOI: 10.1007/s10909-013-0930-6
• 发表时间: 2013
• 期刊: Journal of Low Temperature Physics
• 影响因子: 2
• 作者: Ahlstrom S

Plastic Properties of Solid 4He Probed by a Moving Wire: Viscoelastic and Stochastic Behavior Under High Stress

通过移动导线探测固体 4He 的塑性特性：高应力下的粘弹性和随机行为

• DOI: 10.1007/s10909-013-0922-6
• 发表时间: 2013
• 期刊: Journal of Low Temperature Physics
• 影响因子: 2
• 作者: Ahlstrom S