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.

凝聚态物理学家不断寻找有趣的新物质状态和具有独特可利用特性的新材料，这些特性反映了将它们结合在一起的电子的复杂量子力学相互作用。这些电子特性有时可以近似于材料内移动的单个电子的总和，例如简单金属或硅等半导体中电子的导电性。然而，当对材料的准确描述需要考虑大量电子的集体和相关运动时，这些特性总体上更有趣。这种集体物理学导致了铁等材料的熟悉的铁磁特性，以及不太熟悉的超导现象。在后者中，电子能够流过大部分超导材料而不产生热量，并且极高的电流成为可能。例如，这可用于 MRI 人体扫描仪所需的大型超导磁体。磁性和超导性通常是对立的现象，因为它们涉及电子自旋的不同排列。自旋是电子的一种量子特性，它会产生固有磁场——它可以被想象成附着在每个电子上的微小罗盘针。在铁磁性中，所有自旋都指向同一方向，但在传统超导中，电子形成自旋指向相反方向的电子对（库珀对）。因此，铁磁性通常会通过使它们的自旋平行排列来破坏这些库珀对，从而破坏超导性。凝聚态物理学家经常寻找铁磁性和超导性共存的新材料，因为这可能表明存在某种奇异的新形式的超导性（或其他新颖的量子态）。一个例子是自旋三重态超导，其中库珀对的自旋更喜欢平行排列而不是反平行排列。尝试产生这种奇异物质状态的一种方法是通过在彼此之上沉积非常薄的超导和铁磁薄膜（几纳米厚）来生长人造材料。通过这种方式，可以调整最终结构的特性，有时会导致其表现出在天然存在的散装材料中从未发现的行为。这方面的一个例子是一种独特的自旋三重态（所谓的奇频）超导性，最近在这种类型的薄膜结构中得到了证明。如果还使用先进的电子束光刻技术在薄膜平面上对这种薄膜材料进行图案化，以在纳米尺度上产生额外的图案和结构，那么人造材料的生产可以更进一步。这种方法不仅可以发现有趣的新量子相，还可以带来可在量子计算等未来技术中利用的有用特性。在这个项目中，我们汇集了一支具有多种技能的专家团队，他们可以对上述纳米结构材料类型进行生长、图案化、测量和理论研究。我们的方法的一个特别新颖的方面是使用涉及中子、μ子、X射线和定制扫描磁传感器的强大成像技术，以获得对表现出奇数频率三重态超导性的系统中起作用的基本物理以及详细的磁和物理结构及其奇异特性之间的关系的独特见解。尽管该项目的基本目标是追求新的科学知识，但我们将寻找可能在未来得到应用的有趣效果和特性。

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.

Meissner screening as a probe for inverse superconductor-ferromagnet proximity effects

迈斯纳筛选作为反超导-铁磁体邻近效应的探针

• DOI: 10.1103/physrevb.104.l060506
• 发表时间: 2021
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Flokstra M