Generation, Imaging and Control of Novel Coherent Electronic States in Artificial Ferromagnetic-Superconducting Hybrid Metamaterials and Devices

人造铁磁-超导混合超材料和器件中新型相干电子态的生成、成像和控制

• 批准号: EP/J01060X/1
• 负责人: Stephen Lee
• 金额: $ 73.53万
• 依托单位: University of St Andrews
• 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%2FJ01060X%2F1
• 关键词: Generation; Imaging; Control; Novel; Coherent

Condensed matter physicists are constantly looking for interesting new states of matter and new materials with unique exploitable properties which reflect the complex quantum mechanical interactions of the electrons that bind them together. These electronic properties can sometimes be approximated to the sum of individual electrons moving within the material, such as the electrical conduction of electrons in simple metals or semiconductors like silicon. The properties are on the whole more interesting, however, when an accurate description of the material needs to account for the collective and correlated motion of large numbers of electrons. Such collective physics leads to the familiar ferromagnetic properties of materials like iron and, less familiarly, the phenomenon of superconductivity. In the latter electrons are able to flow through the bulk of a superconducting material without generating heat and extraordinarily high electrical currents become possible. This finds application, for example, in the large superconducting magnets required for MRI body scanners. Magnetism and superconductivity are often antagonistic phenomena, since they involve different arrangements of the spins of electrons. Spin is a quantum property of electrons that gives rise to intrinsic magnetic fields - it can be visualised as a tiny compass needle attached to each electron. In ferromagnetism all the spins point in the same direction, but in conventional superconductivity the electrons form pairs (Cooper pairs) in which the spins point in opposite directions. Ferromagnetism therefore normally destroys these Cooper pairs, and hence superconductivity, by causing their spins to align parallel.Condensed matter physicists often look for new materials where ferromagnetism and superconductivity coexist, since this can suggest the presence of some exotic new form of superconductivity (or other novel quantum state). One example is spin-triplet superconductivity, in which the spins of a Cooper pair prefer to be aligned parallel rather than antiparallel. One way to try and engender such exotic states of matter is to grow artificial materials by depositing very thin superconducting and ferromagnetic films (a few nm thick) on top of one another. In this way the properties of the final structure can be tuned, sometimes leading it to exhibit behaviours that have never been found in naturally occurring bulk materials. An example of this is a unique kind of spin-triplet (so called odd-frequency) superconductivity that has recently been demonstrated in this type of thin film structure. The production of artificial materials can be taken a step further if one also patterns such thin film materials in the plane of the film using advanced electron beam lithography technology, to produce additional patterns and structures on the nanoscale. Such an approach could lead not only to the discovery of interesting new quantum phases, but could also to useful properties that could be exploited in future technologies, such as quantum computing.In this project we bring together a team of experts with a diverse range of skills that can grow, pattern, measure and undertake theoretical studies on the type of nanostructured materials discussed above. One particularly novel aspect of our approach is the use of powerful imaging techniques involving neutron, muons, X-rays and bespoke scanning magnetic sensors to gain unique insights into both the basic physics at play in systems exhibiting odd-frequency triplet superconductivity as well as the relation between the detailed magnetic and physical structures and their exotic properties. Although the basic aim of this project is the pursuit of new scientific knowledge, we will be looking for interesting effects and properties that might find future applications.

冷凝物质物理学家一直在寻找具有独特的可剥削性能的有趣的物质和新材料的新状态，这些特性反映了将它们粘合在一起的电子的复杂量子机械相互作用。这些电子特性有时可以近似于材料中移动的单个电子的总和，例如简单金属中电子的电导传导或硅等半导体。但是，当对材料的准确描述需要说明大量电子的集体和相关运动时，这些属性总体上更有趣。这种集体物理学导致了铁等材料的熟悉的铁磁特性，不太熟悉的超导性现象。在后者中，电子能够在不产生热量和极高的高电流的情况下流过大部分超导材料。例如，在MRI身体扫描仪所需的大型超导磁体中找到了应用。磁性和超导性通常是拮抗现象，因为它们涉及电子旋转的不同排列。自旋是电子的量子特性，产生了固有的磁场 - 可以将其视为连接到每个电子的微小指南针。在铁磁性中，所有旋转都朝着相同的方向指向，但是在常规的超导性中，电子形成对（库珀对），其中旋转指向相反方向。因此，铁磁性通常通过使其旋转与平行对齐来摧毁这些库珀对，因此会摧毁这些库珀对，因此经常寻找的物理学家通常会寻找新材料，在这些新材料中，铁磁性和超导性共同存在，因为这可以表明存在某种异国情调的超导导性新形式（或其他新型新颖的新颖量化状态）。一个示例是自旋三链球超导性，其中库珀对的旋转更喜欢平行对准而不是反平行。尝试产生这种异国物质状态的一种方法是通过将非常薄的超导和铁磁膜（几nm厚）放置在彼此的顶部来种植人造物质。这样，最终结构的特性就可以进行调整，有时会导致其表现出在自然发生的散装材料中从未发现的行为。一个例子是一种独特的旋转三个（所谓的奇数）超导性，最近在这种类型的薄膜结构中已证明。如果使用先进的电子束光刻技术在膜平面上使用这种薄膜材料的模式，则可以将人造材料的产生进一步发展，以在纳米级上产生其他模式和结构。这种方法不仅可能导致有趣的新量子阶段，而且还可以探讨可以在未来技术（例如量子计算）中利用的有用属性。在该项目中，我们将一组专家组合在一起，这些专家团队具有各种各样的技能，这些技能可以在上面讨论的纳米结构材料的类型上成长，模式，测量和进行理论研究。我们方法的一个特别新的方面是，使用涉及中子，MUON，X射线和定制磁磁传感器的功能强大的成像技术，以在系统的系统中具有独特的见解，以介绍具有奇数频率三胞胎超导性的系统中的基本物理，以及详细的磁性和物理结构与其异国情调及其外来属性之间的关系。尽管该项目的基本目的是追求新的科学知识，但我们将寻找可能发现未来应用的有趣效果和属性。

项目成果

Continuously tuneable critical current in superconductor-ferromagnet multilayers

超导铁磁体多层膜中连续可调的临界电流

• DOI: 10.1063/1.4989693
• 发表时间: 2017
• 期刊: Applied Physics Letters
• 影响因子: 4
• 作者: Curran P

Thermodynamic phase transitions in a frustrated magnetic metamaterial.

• DOI: 10.1038/ncomms9278
• 发表时间: 2015-09-21
• 期刊: Nature communications
• 影响因子: 16.6
• 作者: Anghinolfi L;Luetkens H;Perron J;Flokstra MG;Sendetskyi O;Suter A;Prokscha T;Derlet PM;Lee SL;Heyderman LJ
• 通讯作者: Heyderman LJ

Silicide induced surface defects in FePt nanoparticle fcc-to-fct thermally activated phase transition

• DOI: 10.1016/j.jmmm.2016.05.099
• 发表时间: 2016-02
• 期刊: Journal of Magnetism and Magnetic Materials
• 影响因子: 2.7
• 作者: Shu Chen;Stephen Lee;P. André;P. André

Remotely induced magnetism in a normal metal using a superconducting spin-valve

• DOI: 10.1038/nphys3486
• 发表时间: 2016-01-01
• 期刊: NATURE PHYSICS
• 影响因子: 19.6
• 作者: Flokstra, M. G.;Satchell, N.;Lee, S. L.
• 通讯作者: Lee, S. L.

Irreversible magnetization switching at the onset of superconductivity in a superconductor ferromagnet hybrid

• DOI: 10.1063/1.4938467
• 发表时间: 2015-12
• 期刊: Applied Physics Letters
• 影响因子: 4
• 作者: P. Curran;Jang-Whan Kim;N. Satchell;J. Witt;G. Burnell;M. Flokstra;Steve Lee;J. Cooper;C. Kinane;S. Langridge;A. Isidori;N. Pugach;M. Eschrig;S. Bending