International Research Fellowship Program: Infrared and Optical Studies of Quantum Phase Transitions

国际研究奖学金计划使美国科学家和工程师能够在国外进行三到二十四个月的研究。该计划的奖项提供了联合研究的机会，并利用国外独特或互补的设施、专业知识和实验条件。该奖项将支持诺曼·P·阿米蒂奇博士与瑞士日内瓦大学的德克·范德马尔博士合作的为期16个月的研究奖学金。本项目主要研究在所谓的量子相变(QPTS)附近凝聚态系统的光学和红外性质。这是凝聚态物理学中一些最具挑战性和最有趣问题的前沿话题。曾经被认为是理论上的好奇，现在越来越清楚的是，附近的QPTs的存在可能是理解许多处于凝聚态物理前沿的系统的异常行为的关键。人们正在研究相关电子系统的光学和红外响应，例如超导体和新的磁态，因为它们是通过绝对零度附近的各种磁和超导基态之间的这种转变，通过外部参数(例如压力、载流子密度或磁场)进行调谐的。这项工作是由日内瓦大学的德克·范德马雷尔教授团队利用范德马雷尔博士实验室最先进的设施和瑞士光源(SLS)同步加速器目前安装的新红外系统完成的。Van der Marel教授目前的工作集中在使用各种红外和光学光谱探测器研究强关联电子系统的低能激发光谱。日内瓦的实验室为这一项目配备了独特的设备，是世界上进行此类研究的顶级实验室之一。然而，对压力调谐QPTs(如在重费米子系统中发现的那些)的光学研究，需要使用小的束斑来耦合到钻石压腔中。这是一种与传统的基于实验室的红外或光源不兼容的要求，但红外同步辐射(IRSR)光源的出现使其成为可能。该项目的独特之处之一是在SLS使用了新启用的红外光束线。

0402699ArmitageThe International Research Fellowship Program enables U.S. scientists and engineers to conduct three to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.This award will support a sixteen-month research fellowship by Dr. Norman P. Armitage to work with Dr. Dirk van der Marle at the University of Geneva in Switzerland. This project concerns the study of optical and infrared properties of condensed matter systems near so-called quantum phase transition (QPTs). This a topic at the forefront of some of the most challenging and interesting problems in condensed matter physics. Once thought to be a theoretical curiosity, it is becoming increasingly clear that the existence of nearby QPTs may hold the key to understanding the unusual behavior of many systems at the forefront of condensed matter physics. The optical and infrared response of correlated electron systems, such as superconductors and novel magnetic states, are being investigated as they are tuned via an external parameter (e.g. pressure, carrier density, or magnetic field) through such a transition between various magnetic and superconducting ground states near absolute zero temperature. The work is being done in the group of Prof. Dirk van der Marel at the University of Geneva using both the state-of-the-art facilities of Dr. van der Marel's lab and new infrared systems being currently installed at the Swiss Light Source (SLS) synchrotron. Prof. van der Marel's present work concentrates on the low energy excitation spectra of strongly correlated electron systems, using various infrared and optical spectroscopic probes. The lab in Geneva is uniquely equipped for this project as one of the top laboratories in the world for such investigations. However, the optical study of pressure-tuned QPTs (such as those found in heavy fermion systems), necessitates the use of small beam spots for coupling into a diamond anvil pressure cells. This is a requirement incompatible with traditional lab based infrared or optical sources, but made possible by the advent of infrared synchrotron radiation (IRSR) sources. One of the unique aspects of this project is the use of newly commissioned infrared beamlines at the SLS.