CAREER: Correlated States in the Surface of Kondo Insulators

非技术摘要：非常有用的，有时是奇异的功能材料通常来自电子相互作用强烈的固体。这些所谓的“强关联材料”的性质无法从单个电子的详细知识中直接推断出来，因此经常给我们带来惊喜：用于MRI诊断的高温超导体，iPod内部的巨磁阻材料，仅举几例。该项目旨在探索和理解被称为“近藤绝缘体”的一类相关材料表面的新量子态。我们的研究团队已经发现了一种这样的材料SmB 6，它具有一个奇异的金属表面，围绕着真正绝缘的主体，并受到时间反演对称性的保护。这项CAREER资助允许在几个近藤绝缘体上进行晶体生长，测量和设备制造，以揭示表面状态的性质。通过扩展，它们不寻常的电子和热特性可以用于技术应用，如容错量子计算，生物启发的信息处理和量子计量学。该项目纳入了若干教育内容，包括课程编制、中学推广和学生科学培训。特别是，来自圣安娜贫困地区的高中志愿者以及加州大学欧文分校加州少数民族参与计划联盟的本科研究员的科学参与预计将产生兴趣，并为他们在科学和技术方面的职业生涯做好准备。 技术摘要：该CAREER基金资助强相关近藤绝缘体表面态的制造和实验研究。当前凝聚态物理的一个焦点是理解电子关联将给拓扑有序材料带来什么。近藤绝缘体，特别是SmB 6是典型的强关联材料，具有f电子物理和一些非常不寻常的电子特性。最近，拓扑近藤绝缘体理论预测在这些材料中的一些拓扑非平凡的表面状态的存在。随后的实验，包括我们自己的实验已经证明了在SmB 6的金属表面状态和它的拓扑图片的一致性。关于表面状态的确切性质，以及由于表面状态内以及表面和本体之间的相互作用而导致的不寻常性质，仍然存在问题。该项目旨在回答其中的一些问题，并使用近藤绝缘体作为探索电子相关，重费米子物理和拓扑秩序的不寻常量子相位的平台。一个系统的方法，结合晶体生长，运输，光学，热和力的测量是用来揭开表面电子的动力学和能量学，了解表面的热性能，并调查可能的量子相变的化学掺杂，磁场，应变和压力。该项目包括几个重要的教育组成部分。该补助金允许开发研究生物理课程，实验室内的中学推广活动，以及在职业生涯的各个阶段对学生进行培训。即使没有先进的物理知识，来自圣安娜贫困地区的高中志愿者也可以学习和执行晶体生长。一些设备制造是由加州大学欧文分校的加州少数民族参与计划联盟的本科研究人员在我们的集成纳米系统研究设施接受纳米制造培训后进行的。通过这个项目，一个毕业生接受广泛的，但综合培训低温物理，晶体生长和高精度光学仪器，这将准备他/她在未来复杂的学术或工业工作。

Non-technical abstract: Highly useful and sometimes exotic functional materials often emerge from solids where electrons interact strongly with each other. The properties of these so-called "strongly correlated materials" cannot be directly inferred from the detailed knowledge of individual electrons, and therefore often give us pleasant surprises: high temperature superconductors for MRI diagnosis, giant magneto-resistance materials inside iPods, just to name a few. This project aims at exploring and understanding novel quantum states in the surface of a class of correlated materials called "Kondo insulators". One such material SmB6 has already been found, in part by our research team, to host an exotic metallic surface that surrounds the truly insulating bulk and is protected by time-reversal symmetry. This CAREER grant allows crystal growth, measurements and device fabrications on several Kondo insulators in order to unveil the nature of the surface state. By extension their unusual electronic and thermal properties can be exploited for technological applications such as fault-tolerant quantum computing, bio-inspired information processing and quantum metrology. Several educational components are integrated into this project, consisting of course developments, middle school outreach and scientific trainings for students. In particular, the scientific involvements by high school volunteers from disadvantaged regions in Santa Ana, as well as undergraduate researcher from UC Irvine's California Alliance for Minority Participation program are expected to generate interest and prepare them for careers in science and technology. Technical abstract: This CAREER grant funds the fabrication and experimental investigation of surface states in strongly correlated Kondo insulators. A current focus of condensed matter physics is to understand what electron correlation will bring to topologically ordered materials. Kondo insulators, in particular SmB6 are prototypical strongly correlated materials featuring f-electron physics and some quite unusual electronic properties. Recently the theory of topological Kondo insulator has predicted in some of these materials the existence of a topological nontrivial surface state. Subsequent experiments including our own have demonstrated in SmB6 the metallic surface state and its consistency with the topological picture. Questions remain about the exact nature of the surface state, and its unusual properties due to interactions within the surface state and between the surface and bulk. This project aims at answering some of these questions as well as using Kondo insulators as a platform for exploring unusual quantum phases with electron correlation, heavy Fermion physics and topological order. A systematic approach incorporating crystal growth, transport, optical, thermal and force measurements is used to unveil the kinetics and energetics of surface electrons, to understand the thermal properties of the surface, and to investigate the possible quantum phase transitions by chemical doping, magnetic field, strain and pressure. Integrated into this project are several important educational components. The grant allows the development of a graduate physics course, in-lab middle school outreach activities, and the training of students at various stages of their career. The crystal growth can be learnt and performed in part by high school volunteers from disadvantaged regions in Santa Ana even without advanced knowledge of physics. Some of the device fabrication is performed by undergraduate researches from California Alliance for Minority Participation program at UC Irvine, after receiving nano-fabrication trainings in our Integrated Nanosystems Research Facility. Through this project, a gradate student receives broad but integrated trainings on low temperature physics, crystal growth and high precision optical instrumentation, which will prepare him/her for sophisticated academic or industry jobs in the future.