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Un-particle superconductivity in low-dimensional materials

低维材料中的非粒子超导性

基本信息

批准号：
EP/V02986X/1
负责人：
Nigel Hussey
金额：
$ 85.43万
依托单位：
University of Bristol
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2021
资助国家：
英国
起止时间：
2021 至无数据
项目状态：
未结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FV02986X%2F1
关键词：
Un particle superconductivity low dimensional

项目摘要

The phenomenon of superconductivity was discovered over a century ago. Over the course of the 20th century, researchers began to unearth its myriad of remarkable properties, including loss-less, high power electrical transmission, magnetic levitation and Josephson tunneling (used to determine fundamental constants with exquisite accuracy). In the 21st century, superconductivity is widely recognised as a pivotal player in the frontier development of quantum computation. On the theoretical side, the definitive theory of superconductivity was published by Nobel laureates John Bardeen, Leon Cooper and Bob Schrieffer over half a century ago. BCS theory proved to be remarkably successful, not only in explaining the properties of many known superconductors, but also in serving as a guide in the search for new superconductors, even those with an unconventional or anisotropic pairing symmetry. Over time, however, a number of superconducting materials have emerged that appear to challenge the BCS template. Significantly, their superconducting properties appear, in many respects, to be superior. Fundamental to BCS theory is the notion that Cooper pairing is an instability of a 'good' metal composed of coherent electronic states with long mean free path. Over the past few decades, however, superconductivity has also been discovered in 'bad' or 'strange metals', i.e. metals that do not conform to the standard models of metallic behaviour. Bad metals are characterized by an electron mean free path (at high temperatures) that diminishes to a fraction of the interatomic distance, while strange metals exhibit an electrical resistivity that grows linearly with temperature effectively from absolute zero right up to their melting point and a response in a magnetic field that follows an entirely different power law dependence to that seen in conventional metals.The core question now is whether BCS theory can account for the emergence of superconductivity in bad or strange metals or whether an entirely new paradigm is required. The fact that the electronic states in bad and/or strange metals lie at the coherent/incoherent boundary suggests that the condensation energy for superconductivity in these materials may derive from a saving in kinetic energy, rather than a saving in potential energy as is the case for BCS superconductors and that the superfluid condensate may emerge from the incoherent, rather than the coherent part of the electron self-energy. We call this alternative paradigm 'un-particle superconductivity'. The goal of this proposal is to explore the viability of un-particle superconductivity in candidate materials via a joint experimental/theoretical research programme that seeks to develop a theoretical framework for pairing of electronic states formed from the incoherent part of the electron spectral function and to test the resulting predictions with precise measurements of their superfluid density and carrier densities (both coherent and incoherent) in the normal, i.e. non-superconducting state. In total, three distinct material classes have been identified as candidate materials for the realization of un-particle superconductivity: copper-oxide high temperature superconductors, iron chalcogenides and one-dimensional purple bronze. Notably, superconductivity in the cuprates was discovered over 35 years ago, yet despite having been subject to the whole spectrum of experimental and theoretical techniques in condensed matter, smoking-gun evidence for BCS-type superconductivity remains elusive. Moreover, cuprates and iron chalcogenides are the only known materials to superconduct in monolayer form and at ambient pressures at temperatures above the boiling point of liquid nitrogen, making them highly attractive as platforms for future quantum computing devices. Finally, fulfillment of our research goals would lead to a new paradigm for (high temperature) superconductivity, one far-removed from the original BCS template.

超导现象是在世纪以前发现的。在整个世纪，研究人员开始发掘它的无数显着的属性，包括无损耗，高功率电力传输，磁悬浮和约瑟夫森隧道（用于确定基本常数与精致的精度）。在21世纪的世纪，超导被广泛认为是量子计算前沿发展的关键角色。在理论方面，半个多世纪前，诺贝尔奖获得者约翰·巴拉特、莱昂·库珀和鲍勃·施里弗发表了超导性的权威理论。BCS理论被证明是非常成功的，不仅在解释许多已知超导体的性质，而且在寻找新的超导体，甚至是那些具有非常规或各向异性配对对称性的超导体方面也是一个指导。然而，随着时间的推移，出现了一些超导材料，似乎挑战BCS模板。值得注意的是，它们的超导性能在许多方面都是上级的。BCS理论的基本概念是，库珀配对是由具有长平均自由程的相干电子态组成的“好”金属的不稳定性。然而，在过去的几十年里，超导性也在“坏”或“奇怪的金属”中被发现，即不符合金属行为标准模型的金属。坏金属的特征是电子平均自由程（在高温下）减少到原子间距离的一小部分，而奇怪的金属表现出电阻率随温度线性增长，从绝对零度一直到熔点，在磁场中的响应遵循与传统金属完全不同的幂律依赖关系。现在的核心问题是，BCS理论可以解释坏的或奇怪的金属中超导性的出现，或者是否需要一个全新的范式。坏金属和/或奇怪金属中的电子态位于相干/非相干边界的事实表明，这些材料中超导性的凝聚能可能来自动能的节省，而不是BCS超导体的势能节省，并且超流凝聚可能来自电子自能的非相干部分，而不是相干部分。我们称这种替代范式为“非粒子超导性”。该提案的目标是通过一项联合实验/理论研究计划探索候选材料中非粒子超导性的可行性，该计划旨在开发一个理论框架，用于从电子光谱函数的非相干部分形成的电子态配对，并通过精确测量其超流密度和载流子密度来测试由此产生的预测。（相干的和非相干的）正常的，即非超导状态。总的来说，三种不同的材料类别已被确定为实现非粒子超导性的候选材料：氧化铜高温超导体，铁硫属化物和一维紫青铜。值得注意的是，铜氧化物中的超导性在35年前就被发现了，然而，尽管在凝聚态物质中进行了整个实验和理论技术的研究，BCS型超导性的确凿证据仍然难以捉摸。此外，铜酸盐和铁硫属化物是唯一已知的以单层形式和在环境压力下在液氮沸点以上的温度下超导的材料，这使得它们作为未来量子计算设备的平台非常有吸引力。最后，我们的研究目标的实现将导致一个新的（高温）超导范例，一个远离原始BCS模板。

项目成果

期刊论文数量（5）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Enhanced Superconducting Pairing Strength near a Pure Nematic Quantum Critical Point

DOI：
10.1103/physrevx.13.011032
发表时间：
2022-02
期刊：
Physical Review X
影响因子：
12.5
作者：
K. Mukasa;K. Ishida;S. Imajo;M. Qiu;M. Saito;K. Matsuura;Y. Sugimura;S. Liu;Y. Uezono;T. Otsuka;M. Čulo;S. Kasahara;Y. Matsuda;N. Hussey;T. Watanabe;K. Kindo;T. Shibauchi
通讯作者：
K. Mukasa;K. Ishida;S. Imajo;M. Qiu;M. Saito;K. Matsuura;Y. Sugimura;S. Liu;Y. Uezono;T. Otsuka;M. Čulo;S. Kasahara;Y. Matsuda;N. Hussey;T. Watanabe;K. Kindo;T. Shibauchi

High-temperature superconductivity and strange metallicity: Simple observations with (possibly) profound implications