Quasiparticle Scattering and Tunneling Spectroscopic Studies on Kondo Lattices, Topological Insulators and Superconductors

*非技术摘要*理解新的电子态是如何出现的，已成为凝聚态物理学的中心研究课题。确定这类电子物质的组织原则将有助于发现具有新颖和有用功能的材料。这个项目的目标是在两个不同的场所研究这个主题：近藤晶格和拓扑材料。在所谓的Kondo晶格中，局域态与巡回电子的纠缠导致了一种在低温下质量大大提高的新型电子态。我们将详细研究这一过程是如何发生的，以及它与进一步转变为有序状态的关系。为此，将采用测量技术来探测电子波如何在这样的系统中干扰。新的电子态，称为拓扑态，不能连续转换为普通态，可以存在于某种类型的材料中，并且它们具有奇特的性质，例如在其边界上导电而不耗散，同时充当绝缘体，在整体中传输。在这个项目中，将使用类似的测量技术来探索在这些拓扑态中诱导的超导电性的性质，以及可能有助于未来构建量子计算机的难以捉摸的Majorana粒子。研究生和本科生将通过进行实验和数据分析以及参加研讨会/会议来传播结果。近年来，人们对理解新颖量子物质的组织原理的兴趣重新燃起。这个项目旨在揭示近藤晶格和拓扑材料中涌现现象的潜在机制。长期以来，URu2Si2中隐藏的有序相一直无视对其有序参数的明确确定。为了解决这个问题，我们将利用准粒子散射和隧穿等光谱技术来研究定域态和巡游带之间的详细杂交过程及其与隐藏有序跃迁的关系。其他密切相关的近藤晶格系统也将被研究。由于非常规能带结构和费米表面拓扑的共同作用，出现了新的拓扑电子态。了解它们背后的物理原理是一个前沿的研究课题。在这个项目中，将使用隧道光谱和其他相敏测量来探索拓扑材料中邻近感生超导电性的性质以及预测存在于此类系统中的Majorana费米子。研究生和本科生将通过进行实验和数据分析以及参加研讨会/会议来传播结果，从而参与这一项目。

****NON-TECHNICAL ABSTRACT****Understanding how novel electronic states emerge has become a central research topic in condensed matter physics. Identifying the organizing principles for such electronic matter will facilitate discovering materials with novel and useful functionalities. The goal of this project is to investigate this theme in two separate venues: Kondo lattices and topological materials. An entanglement of localized states with itinerant electrons in a so-called Kondo lattice leads to a novel electronic state with greatly enhanced mass at low temperature. How exactly this process occurs and its relationship to a further transition into an ordered state will be studied in detail. For this purpose, measurement techniques to probe how electron waves interfere in such a system will be employed. Novel electronic states, called topological, that cannot be continuously transformed to ordinary states can exist in a certain class of materials and they are known to exhibit exotic properties, such as conducting electricity on their boundaries without dissipation while behaving as insulators for transport through the bulk. In this project, the nature of superconductivity induced in these topological states and the elusive Majorana particles that could potentially help in building a quantum computer in the future, will be probed using similar measurement techniques. Graduate and undergraduate students will take parts in this project by carrying out experiments and data analysis and attending workshops/conferences to disseminate the results.****TECHNICAL ABSTRACT****Recent years have witnessed resurging interest in understanding the organizing principles for novel quantum matter. This project aims at unraveling the underlying mechanism for emergent phenomena in Kondo lattices and topological materials. The hidden order phase in URu2Si2 has long defied an unambiguous determination of its order parameter. Towards resolving this problem, the detailed hybridization process between localized states and itinerant bands and its relationship to the hidden order transition will be investigated using spectroscopic techniques such as quasiparticle scattering and tunneling. Other closely related Kondo lattice systems will also be studied. Novel topological electronic states emerge due to a combined effect of unconventional band structure and Fermi surface topology. Understanding their underlying physics is a frontier research topic. In this project, the nature of proximity-induced superconductivity in topological materials and Majorana fermions predicted to exist in such systems will be probed using tunneling spectroscopy and other phase-sensitive measurements. Graduate and undergraduate students will take parts in this project by carrying out experiments and data analysis and attending workshops/conferences to disseminate the results.