Microwave spectroscopy of unconventional metals, superconductors and insulators

非常规金属、超导体和绝缘体的微波光谱

• 批准号: 261622-2013
• 负责人: Broun, David
• 金额: $ 2.99万
• 依托单位: Simon Fraser University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=633517
• 关键词: Microwave; spectroscopy; unconventional; metals; superconductors

Society is currently reaping the benefits of the revolution in semiconductor electronics that occurred after the quantum behaviour of noninteracting electrons was understood in the early 20th century. It is the hope of many researchers around the world that there will be a second revolution in electronic materials when we understand a far more difficult quantum problem - the behaviour of systems of strongly interacting electrons. At this stage the challenges are fundamental: to understand how the important electronic properties emerge in systems of interacting electrons, and to harness these materials so that they produce the desired properties in a controlled way. Many of these materials display unusual forms of superconductivity, a state of matter in which all electrical resistance vanishes. Examples include the cuprate high temperature superconductors; the so-called "heavy fermion" materials, in which electrons appear to be 100 to 1000 times heavier than normal; and the recently discovered iron-based superconductors. At present, the mechanism responsible for superconductivity is not well understood in any of these materials. In addition, the nonsuperconducting states are unusual metals that pose some of the greatest challenges to our understanding of electrons in solids. Our research group has set up a novel facility for carrying out microwave spectroscopy of these materials that is the only one of its kind in the world. Measurements can be performed at temperatures down to 0.05 K, in magnetic fields up to 9 tesla, and at frequencies up to 25 GHz. Microwave fields are used to accelerate the electrons in order to probe their inertial response; and to study their collisions with impurities and with one another. Using this information we are able to understand the structure and dynamics of these novel electronic states. We are also developing new experimental tools, including systems for detecting and quantifying subtle signs of time-reversal-symmetry breaking, an effect that has important applications in magnetism, semiconductors, unconventional superconductors, and so-called topological insulators - materials that are electrically insulating in the bulk, but form robust and highly conducting surface states.

世纪初，人们理解了非相互作用电子的量子行为，之后发生了半导体电子学革命，社会目前正在从中获益。世界各地的许多研究人员都希望，当我们理解了一个困难得多的量子问题--强相互作用电子系统的行为时，电子材料将发生第二次革命。在这个阶段，挑战是根本性的：了解重要的电子特性如何出现在相互作用的电子系统中，并利用这些材料，使它们以可控的方式产生所需的特性。这些材料中的许多显示出不寻常的超导形式，即所有电阻都消失的物质状态。例子包括铜酸盐高温超导体;所谓的“重费米子”材料，其中电子似乎比正常重100至1000倍;以及最近发现的铁基超导体。目前，在这些材料中，负责超导性的机制还没有得到很好的理解。此外，非超导态是不寻常的金属，对我们理解固体中的电子构成了一些最大的挑战。我们的研究小组已经建立了一个新的设备，用于对这些材料进行微波光谱分析，这是世界上唯一的一个。测量可以在温度低至0.05 K，磁场高达9特斯拉，频率高达25 GHz的条件下进行。微波场被用来加速电子，以探测它们的惯性响应，并研究它们与杂质以及彼此之间的碰撞。利用这些信息，我们能够理解这些新的电子态的结构和动力学。我们还在开发新的实验工具，包括用于检测和量化时间反演对称性破缺的微妙迹象的系统，这种效应在磁性，半导体，非常规超导体和所谓的拓扑绝缘体中具有重要的应用-材料是电绝缘体，但形成坚固和高导电的表面状态。