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Controlling unconventional properties of correlated materials by Fermi surface topological transitions and deformations.

通过费米表面拓扑转变和变形控制相关材料的非常规性质。

基本信息

批准号：
EP/P002811/1
负责人：
Joseph Betouras
金额：
$ 44.56万
依托单位：
Loughborough University
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2016
资助国家：
英国
起止时间：
2016 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FP002811%2F1
关键词：
Controlling unconventional properties correlated materials

项目摘要

Widespread electronic technologies of the last few decades have been led by perfecting control over response of electrons in materials where interactions between them are essentially weak. This can now be reliably achieved, e.g., in simple metals and semiconductors, by tuning the Fermi surface and the effective electron mass. However, this technology has reached the limit of its potential due to the fundamentally limited range of electronic properties exhibited by such materials. A dramatic breakthrough can be achieved if one establishes reliable control over collective electronic behaviour in systems where strong interactions between electrons give rise to intriguing macroscopic quantum phenomena. Multiferroics, giant magnetoresistance in spintronic materials, electron correlations in polymeric systems, and high-temperature superconductivity are just are a few examples with vast potential for novel applications. A quantum computer, expected to revolutionise the modern world, and well-envisaged in principle, can still not be realised due to the lack of reliably controlled material base. The reason, largely, is that a priori accurate theoretical underpinning of electron correlation physics, which would allow to design desired electronic properties at will, has remained a challenge and is currently missing.In light of very recent developments of new accurate numerical tools for correlated systems, it is extremely timely to use the new methodology to address properties of certain correlated materials of great technological potential, which are currently in the focus of extensive experimental studies. In this project, cutting-edge numerics and advanced analytical techniques will allow us to develop a definitive and quantitative theoretical picture of key effects and mechanisms associated with quantum phase transitions in correlated electron systems, thereby enabling a priori control over the corresponding material properties. Specifically, we propose a comprehensive theoretical study of effects of deformations of the Fermi surface in the correlated regime by changing external parameters and the resulting emergence of new phases with unconventional physical behaviour. Our main goals are to: (i) gain quantitative understanding of the mechanisms and consequences of Fermi surface reconstruction and Lifshitz topological transitions in correlated-electron model systems, especially those with spin orbit coupling, and their relation to instabilities, under changes of chemical composition or magnetic field or application of pressure; (ii) accurately predict properties of specific benchmark materials of great technological importance, which exhibit intriguing behaviour associated with changes of the Fermi surface and are the focus of current experiments, such as strontium ruthenates, strontium iridates, and fermonic superconductors. (iii) make specific proposals for experiments on those materials to test new theories, (iv) ultimately, achieve reliable control over the properties of these classes of correlated materials.This is fundamental research with direct relevance to development of technology since our choice of the benchmark materials covers a wide range of potential applications. Superconducting SrRu2O4 is expected to harbour the Majorana bound states, making it a candidate for realising qubits of topological quantum computers. Strontium iridates feature a delicate interplay between spin-orbit coupling and Mott physics, which can lead to new-generation spintronic devices, while control over properties of superconductors under pressure, will open new avenues for the superconducting industry.

过去几十年来，电子技术的广泛应用是通过完善对材料中电子响应的控制来实现的，因为材料之间的相互作用本质上很弱。现在可以通过调整费米表面和有效电子质量来可靠地实现这一点，例如在简单金属和半导体中。然而，由于此类材料所表现出的电子特性范围从根本上有限，该技术已达到其潜力的极限。如果在电子之间的强相互作用引起有趣的宏观量子现象的系统中建立对集体电子行为的可靠控制，则可以实现巨大的突破。多铁性、自旋电子材料中的巨磁阻、聚合物系统中的电子相关性和高温超导只是具有巨大新应用潜力的几个例子。量子计算机有望彻底改变现代世界，并且在原理上设想良好，但由于缺乏可靠控制的物质基础，仍然无法实现。究其原因，很大程度上是因为电子相关物理的先验精确理论基础仍然是一个挑战，目前还缺乏这种基础，该理论基础允许随意设计所需的电子特性。鉴于相关系统的新型精确数值工具的最新发展，使用新方法来解决某些具有巨大技术潜力的相关材料的特性是非常及时的，这些材料目前是广泛实验研究的焦点。在这个项目中，尖端的数值和先进的分析技术将使我们能够开发出与相关电子系统中量子相变相关的关键效应和机制的明确和定量的理论图景，从而能够对相应的材料特性进行先验控制。具体来说，我们提出了一项全面的理论研究，通过改变外部参数来研究相关区域中费米面变形的影响以及由此产生的具有非常规物理行为的新相。我们的主要目标是：（i）定量了解相关电子模型系统中费米表面重构和 Lifshitz 拓扑跃迁的机制和后果，特别是那些具有自旋轨道耦合的系统，以及它们在化学成分或磁场或压力变化下与不稳定性的关系； (ii) 准确预测具有重大技术重要性的特定基准材料的特性，这些材料表现出与费米表面变化相关的有趣行为，是当前实验的焦点，例如钌酸锶、铱酸锶和费米超导体。（iii）对这些材料的实验提出具体建议，以测试新理论，（iv）最终实现对这些类别相关材料的性能的可靠控制。这是与技术发展直接相关的基础研究，因为我们选择的基准材料涵盖了广泛的潜在应用。超导 SrRu2O4 预计将具有马约拉纳束缚态，使其成为实现拓扑量子计算机量子位的候选材料。铱铱具有自旋轨道耦合和莫特物理之间微妙的相互作用，这可以产生新一代自旋电子器件，同时控制压力下超导体的性能，将为超导行业开辟新的途径。