Topological superfluids under engineered nanofluidic confinement: new order parameters and exotic excitations

工程纳米流体约束下的拓扑超流体：新序参数和奇异激发

• 批准号: EP/J022004/1
• 负责人: John Saunders
• 金额: $ 145.31万
• 依托单位: Royal Holloway University of London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2012
• 资助国家: 英国
• 起止时间: 2012 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FJ022004%2F1
• 关键词: Topological; superfluids; under; engineered; nanofluidic

Experiments on liquid helium-three near the absolute zero of temperature have played a key role in the development of many central concepts in condensed matter physics. The discovery of superfluid 3He gave us the first p-wave superfluid, a model for unconventional superconductivity, in which the pairing breaks the symmetry of the parent normal metal. Since that time the international programme of materials discovery has thrown up many new unconventional superconductors. And formally the phases of superfluid 3He can be regarded as a quantum vacua, with parallels in particle physics and cosmology [see "The Universe in a Helium Droplet", G.E.Volovik].Recently the topology (in momentum space) of condensed matter systems has been widely applied as a powerful scheme for their classification, alongside the concept of broken symmetry. The simple truths of topology (eg a sphere's surface cannot be continuously deformed into that of a torus) have a powerful impact when applied to complex interacting quantum systems, by pointing to phenomena that must be there, independent of microscopic details; robust protection is conferred by the inviolable constraints of topology. This may lead to electronic devices whose operation relies on the laws of quantum mechanics in a way immune to environmental disturbance, a vision that is supported by Microsoft's Station Q and associated programmes.In this programme we will study the topological superfluidity of helium-three confined in regular nanofabricated geometries, as a model system to further our understanding of topological quantum matter. Our experiments will exploit the recent technical breakthroughs we have made in quantum nanofluidics, and the development of sensitive NMR techniques based on the detection of the precessing magnetic signal by SQUIDs (Superconducting Quantum Interference Devices).Confinement of superfluid 3He in a slab-like cavity of thickness of order the diameter of the Cooper pairs, has a profound effect on the superfluid order and is expected to stabilize new superfluid states of matter. The compressibility of 3He allows the pair diameter to be pressure-tuned, varying the effective confinement. Regular geometries can be fabricated with well-characterized surfaces, which can be tuned in situ by plating with a helium-4 film. This exquisite geometrical control and tuneability, coupled to the ideal material qualities of superfluid 3He, and highly developed microscopic models provide a rigorous theory-experiment interface. Phases with different topologies are expected to be stable under different conditions, and we will map the effect of our new control parameter, confinement, on these phases. We will quantify the role of disorder, arising from surface roughness, and the importance of quantum size effects. These topological superfluids support novel excitations at the faces or edges of the cavity, at domain walls and vortices. The precise character of these excitations depends on whether the superfluid ground state preserves or breaks time reversal symmetry. At the surface of the B-phase they are propagating Majorana fermions, and we will search for these as part of the project.This project has a strong international collaborative dimension, both experimental and theoretical, closely partnering with Cornell and Northwestern in the USA, and PTB (Berlin) in Germany, and exploiting our membership of the European Microkelvin Collaboration. We will connect with other programmes on topological quantum matter in the UK and internationally, enhanced by the Hubbard Theory Consortium, through its visitors programmes and workshops.The project is expected to lead to fundamental insights into topological quantum matter and topological superfluidity/superconductivity in particular. It will drive the innovation of new instrumentation at the new frontier combining ultra-low temperatures and nanoscience, and new SQUID NMR techniques of broad applicability.

在接近绝对零度的温度下对液态氦- 3进行的实验在凝聚态物理学中许多核心概念的发展中发挥了关键作用。超流体的发现他给了我们第一个p波超流体，这是一个非常规超导的模型，在这个模型中，配对打破了母体正常金属的对称性。从那时起，国际材料发现计划已经提出了许多新的非常规超导体。在形式上，超流体3He的相可以被看作是一个量子真空，在粒子物理学和宇宙学中有相似之处（参见《氦滴中的宇宙》，G.E.Volovik）。近年来，凝聚态系统的拓扑（动量空间）与对称性破缺的概念一起被广泛应用于它们的分类。拓扑学的简单真理（例如球体的表面不能连续地变形成环面）在应用于复杂的相互作用量子系统时具有强大的影响，通过指出必须存在的现象，独立于微观细节；鲁棒性保护是由不可违背的拓扑约束赋予的。这可能会导致电子设备的运行依赖于量子力学定律，在某种程度上不受环境干扰，微软的Station Q和相关程序支持了这一愿景。在这个项目中，我们将研究氦- 3在规则纳米几何结构中的拓扑超流动性，作为一个模型系统，以进一步我们对拓扑量子物质的理解。我们的实验将利用我们最近在量子纳米流体方面取得的技术突破，以及基于squid（超导量子干涉装置）检测进路磁信号的敏感核磁共振技术的发展。将超流体3He限制在厚度为库珀对直径数量级的板状腔中，对超流体的秩序有深远的影响，并有望稳定物质的新超流体状态。3He的可压缩性允许对直径进行压力调节，从而改变有效约束。规则的几何形状可以制造出具有良好特征的表面，这些表面可以通过镀上氦-4薄膜在原位调谐。这种精致的几何控制和可调性，加上超流体3He的理想材料质量，以及高度发达的微观模型提供了严格的理论-实验界面。具有不同拓扑结构的相在不同的条件下是稳定的，我们将映射我们的新控制参数约束对这些相的影响。我们将量化由表面粗糙度引起的无序的作用，以及量子尺寸效应的重要性。这些拓扑超流体支持在腔面或边缘、畴壁和涡流处的新激励。这些激发的精确特征取决于超流体基态是否保持或破坏时间反转对称性。在b相的表面，它们正在传播马约拉纳费米子，我们将寻找这些费米子作为项目的一部分。该项目具有强大的国际合作维度，包括实验和理论，与美国康奈尔大学和西北大学以及德国PTB（柏林）密切合作，并利用我们的欧洲微开尔文协作成员。我们将通过哈伯德理论联盟的访客项目和研讨会，与英国和国际上其他关于拓扑量子物质的项目建立联系。该项目预计将导致对拓扑量子物质和拓扑超流动性/超导性的基本见解。它将推动结合超低温和纳米科学的新前沿新仪器的创新，以及新的适用广泛的SQUID核磁共振技术。

项目成果

Path-Dependent Supercooling of the $^3$He Superfluid A-B transition

$^3$He 超流体 A-B 转变的路径相关过冷

• DOI: 10.48550/arxiv.2012.14044
• 发表时间: 2020
• 作者: Lotnyk D

Realizing Quantum Materials with Helium: Helium films at ultralow temperatures, from strongly correlated atomically layered films to topological superfluidity

用氦实现量子材料：超低温下的氦薄膜，从强相关原子层状薄膜到拓扑超流性

• DOI: 10.48550/arxiv.1910.01058
• 发表时间: 2019
• 作者: Saunders J

A microkelvin cryogen-free experimental platform with integrated noise thermometry

• DOI: 10.1088/1367-2630/15/11/113034
• 发表时间: 2013-11-15
• 期刊: NEW JOURNAL OF PHYSICS
• 影响因子: 3.3
• 作者: Batey, G.;Casey, A.;Shibahara, A.
• 通讯作者: Shibahara, A.

Current Sensing Noise Thermometry: A Fast Practical Solution to Low Temperature Measurement

• DOI: 10.1007/s10909-014-1147-z
• 发表时间: 2014-06-01
• 期刊: JOURNAL OF LOW TEMPERATURE PHYSICS
• 影响因子: 2
• 作者: Casey, A.;Arnold, F.;Matthews, A. J.
• 通讯作者: Matthews, A. J.