Electronic Structure of Unconventional Spin-Orbit Materials

非技术摘要：在普通绝缘体(如钻石)中，被占据的电子能级与未被占据的电子能级被称为能隙的大能垒分开。当施加电场时，能隙防止电流流动。最近的研究发现了一类新的绝缘体，称为拓扑绝缘体和相关的狄拉克材料，在这种材料中，电子可以通过向外移动到绝缘体的表面来绕过能隙。这些不寻常的电子在表面上运动的能量与速度的行为类似于光，遵循狄拉克方程。它们表现出许多不同寻常的量子性质，可以用来改进基于自旋的电子学、新形式的量子计算和长期而言的节能设备。本项目致力于研究电子在表面运动的新的量子行为的细节，这不仅将有助于更好地理解这种行为的机制，而且可能发现新的应用途径。从事这个项目的学生发展真空和纳米技术、材料表征方法以及先进的X射线光学和电子能谱技术方面的专业知识，为他们在工业、学术界或政府实验室的科学职业生涯做准备。“量子材料”推广项目及其与普林斯顿REU和其他项目的整合，如“领导力联盟项目：致力于增加学术界的多样性”，吸引了许多少数民族和年轻学生，并促进他们进入令人兴奋的现代科学世界。技术摘要：发现具有有用的电子或磁性的物质的新相是现代物理学的一个重要目标。在过去的几年里，研究发现了狄拉克材料的一种新阶段，被称为“拓扑绝缘体”。它们在没有磁场的情况下表现出类似量子霍尔的效应，并且可以在室温下工作。在拓扑绝缘体中，这些效应导致表面态具有不寻常的自旋织构，其能量和动量之间存在线性关系(狄拉克色散)。据预测，这种状态将产生无耗散(节能)自旋电流、量子纠缠和新的宏观行为，这些行为遵循轴离子电动力学而不是麦克斯韦方程，并可能实现可用于容错量子计算的奇异粒子。利用角度分辨光电子能谱研究了几种Bi基2D和3D Dirac材料的量子性质，以及它们的磁性和超导掺杂引起的相互作用和关联效应。当发现具有类似性质的新材料时，他们也会被联合起来研究，并与以前已知的材料进行比较。从事这个项目的学生发展真空和纳米技术、材料表征方法、先进的X射线光学和自旋和光子偏振分辨电子光谱技术方面的专业知识，为他们未来在工业、学术界或政府实验室的科学职业生涯做准备。推广项目“量子材料”及其与普林斯顿REU和其他项目的整合，如“领导力联盟项目：致力于增加学术界的多样性”，吸引了许多少数族裔和年轻学生，帮助他们进入令人兴奋的现代科学世界。

Nontechnical Abstract: In an ordinary insulator, such as diamond, the occupied electronic levels are separated from unoccupied levels by a large energy barrier known as an energy gap. The energy gap prevents current flow when an electric field is applied. Recent research has uncovered a new class of insulators, called topological insulators and related Dirac materials, in which electrons can bypass the energy gap by moving out to the surfaces of the insulator. The energy vs. velocity behavior of these unusual electrons moving on the surface is light-like and follows Dirac equation. They exhibit many unusual quantum properties which can be harnessed to improve spin-based electronics, novel forms of quantum computing and energy-efficient devices in the longer run. This project focuses on studying the details of the novel quantum behaviors of electrons moving on the surface which will in turn not only lead to better understanding of the mechanism for doing so but also likely discover new pathways to applications. Students working on this project develop expertise in vacuum and nano-technology, material characterization methodologies, and advanced x-ray optics and electronic spectroscopy techniques preparing them for scientific careers in industry, academia or government laboratories. Outreach programs "Quantum Materials" and their integration with Princeton's REU and others such as "The Leadership Alliance Program: dedicated to increase diversity in academia" involve many minority and young students and facilitate their entry into the exciting world of modern science.Technical Abstract: Discovering new phases of matter with useful electronic or magnetic properties is an important goal in modern physics. In the past few years, research has uncovered a new phase of Dirac material dubbed "Topological Insulators". They exhibit quantum Hall-like effects without magnetic field and can be operated at room temperatures. In a topological insulator, these effects lead to surface states that have unusual spin textures with a linear relationship between energy and momentum (Dirac dispersion). Such states have been predicted to give rise to dissipationless (energy saving) spin currents, quantum entanglements and novel macroscopic behavior that obeys axionic electrodynamics rather than Maxwell's equations and can potentially realize exotic particles that can be used for fault tolerant quantum computing. Angle-resolved photoemission spectroscopy is used to study the quantum properties of several Bi-based 2D and 3D Dirac materials and their magnetic and superconducting doping-induced interaction and correlation effects under this project. When new materials with similar properties are discovered they are also studied in concert and compared with previously known materials. Students working on this project develop expertise in vacuum and nano-technology, material characterization methodologies, and advanced x-ray optics and spin- and photon-polarization resolved electronic spectroscopy techniques preparing them for future scientific careers in industry, academia or government laboratories. Outreach programs "Quantum Materials" and their integration with Princeton's REU and others such as "The Leadership Alliance Program: dedicated to increase diversity in academia" involve many minority and young students and facilitate their entry into the exciting world of modern science.