CAREER: BROADBAND INFRARED NANO-SPECTROSCOPY

相关电子材料中的竞争相互作用会导致涌现现象，例如，在温度、化学掺杂和电场等外部扰动下的相变。我们将研究具有强相互作用的氧化物中的金属-绝缘体相变，例如二氧化钒和具有钙钛矿结构的锰氧化物。我们将主要使用红外光子来记录相变在纳米尺度和宏观长度尺度上的演化，使用宽带远场和近场红外光谱。我们的目标是发现管理具有强烈相互作用的材料中出现的新范式。具体地说，我们希望确定系统的大小对金属-绝缘体相变和伴随的结构不稳定性的演化所起的作用。我们计划发展具有宽带远红外光子的近场纳米光谱，以便以大约10纳米的空间分辨率同时记录电子和结构变化。这种实验方法将在物理、化学、生物、光学工程和材料科学中具有广泛的适用性，超越了对相关电子材料的应用。该项目将为研究生和本科生提供高级科学培训，从而为他们未来在学术机构、国家和私人研究实验室的职业生涯奠定良好的基础。*固体中大量电子之间的强相互作用导致新的宏观行为，这在弱相互作用的材料中是看不到的。这种奇异的宏观现象的例子包括金属-绝缘体相变，高温超导，以及磁、电子和结构的耦合有序。宏观组织的原则并不以任何简单的方式遵循管理单个量子实体(即单电子)的已知物理定律。在复杂的、相互作用的系统中，规范集体行为和秩序现象的规则尚未被发现，这就是我研究这类系统的动机。我们将主要使用红外光子来研究复杂金属氧化物中的金属-绝缘体相变和有序现象。光子与带电的量子粒子相互作用，并携带有关其行为的信息，我们对这些信息进行测量和记录。由于组织原则可以随着系统大小的不同而变化，我们计划研究从纳米尺度(数百个原子)到宏观尺寸(万亿个原子)的金属绝缘体相变。我们计划开发近场光学光谱学的实验工具，通过耦合到一个广泛的低能红外光子连续谱来研究多方面的纳米现象。该项目将为研究生和本科生提供高级科学培训，从而为他们未来在学术机构、国家和私人研究实验室的职业生涯奠定良好的基础。

****Technical Abstract****Competing interactions in correlated electron materials lead to emergent phenomena, for example, phase transitions under external perturbations like temperature, chemical doping, and electric field. We will investigate metal-insulator phase transitions in oxides with strong interactions, for example, vanadium dioxide, and manganites with perovskite structure. We will primarily use infrared photons to document the evolution of the phase transformations at nanometer length scales and macroscopic length scales using broadband far-field and near-field infrared spectroscopy. The goal is to discover new paradigms that govern emergence in materials with strong interactions. Specifically, we hope to ascertain the role of size of the system on the evolution of metal-insulator phase transformations and accompanying structural instabilities. We plan to develop near-field nano-spectroscopy with broadband far-infrared photons in order to simultaneously document electronic and structural changes with about 10 nm spatial resolution. This experimental method will have wide applicability in physics, chemistry, biology, optical engineering and materials science that goes beyond the applications to correlated electron materials. This project will provide advanced scientific training for graduate and undergraduate students, and hence an excellent foundation for their future careers in academic institutions, and national and private research laboratories.****Non-Technical Abstract****Strong interactions between a large number of electrons in solids lead to novel macroscopic behavior that is not seen in materials with weak interactions. Examples of such exotic macroscopic phenomena include metal-insulator phase transitions, superconductivity at high temperatures, and coupled magnetic, electronic and structural ordering. The principles of macroscopic organization do not follow in any simple manner from the known laws of physics that govern individual quantum entities (i.e. single electrons). The rules that regulate collective behavior and ordering phenomena in complex, interacting systems are yet to be discovered, and this is what motivates my research on such systems. We will primarily use infrared photons to investigate metal-insulator phase transitions and ordering phenomena in complex metal oxides. The photons interact with charged quantum particles and carry information about their behavior which we measure and record. Since organizational principles can vary with the size of the system, we plan to study metal-insulator phase transformations from nanometer length scales (hundreds of atoms) to macroscopic sizes (trillion trillion atoms). We plan to develop the experimental tool of near-field optical spectroscopy by coupling to a broad continuum of low energy infrared photons in order to study multi-faceted nanoscale phenomena. This project will provide advanced scientific training for graduate and undergraduate students, and hence an excellent foundation for their future careers in academic institutions, and national and private research laboratories.