Photoemission Experiments of Correlated Electron Systems

高分辨角度分辨光电子能谱(ARPES)将被用来研究相关电子系统的电子结构，特别是巨磁阻氧化物和高T_c超导体。该项目将利用先进光源光束线12的一个新的高分辨率终端站，以及科罗拉多州独特的基于激光的光电发射系统。这两种装置都带来了出色的光谱分辨率，与标准的ARPES实验相比，激光器还可以降低表面灵敏度。这种降低的表面灵敏度应该能够将ARPES实验扩展到更广泛的材料，如高T_c超导体YBA(2)Cu(3)O(7)，这些材料不具有良好的切割性能。此外，在被认为解理良好的表面上，测量应该更不受样品老化的影响。这将克服ARPES的主要局限性之一，使数据更清晰、更可信，最终可能回答诸如高温超导体中配对相互作用的起源等基本问题。该活动的一个重要组成部分是对学生进行光学、固体物理和同步辐射领域的跨学科培训。此外，P.I.还领导了一项REU(本科生研究体验)计划，并将继续让本科生参与这项研究。爱因斯坦因光电效应而获得诺贝尔奖，光电效应是指入射光子(单个光包)从固体中射出电子。这项技术已经成熟，可以说是对固体中电子的量子力学状态的最强大的探测器。这一个人研究人员奖支持一个项目，该项目将应用这项技术来研究一些最有趣和潜在有用的固体--高温超导体(对电流具有零阻力的材料)和巨大的磁阻氧化物(如果对样品施加磁场，它们的电阻会发生“巨大”变化的材料)。我们的目标是了解这些材料中的基本量子力学相互作用，这些相互作用是导致材料独特的电磁性能的原因。将利用两个新的和强大的源来产生将在实验中使用的光子。其中一个是位于伯克利的先进光源的新光束线，这是美国卓越的同步辐射设备，可以产生软X射线。另一个是激光系统，PI的研究小组在他们的实验室里建造了这个系统。有了这个自制的系统，该团队已经做出了他们认为是基于激光的角度分辨光电子能谱的第一个演示。该活动的一个重要组成部分是对学生进行光学、固体物理和同步辐射领域的跨学科培训。此外，P.I.还领导了一项REU(本科生研究体验)计划，并将继续将本科生纳入这项研究。

High resolution angle resolved photoemission (ARPES) will be used to study the electronic structure of correlated electron systems, particularly colossal magnetoresistive (CMR) oxides and high Tc superconductors. The project will utilize a new high resolution endstation at the Advanced Light Source beamline 12, as well as a unique laser-based photoemission system in Colorado. Both setups bring excellent spectral resolution, with the laser additionally allowing reduced surface sensitivity compared to standard ARPES experiments. This reduced surface sensitivity should enable the extension of ARPES experiments to a wider range of materials such as the high Tc superconductor YBa(2)Cu(3)O(7) which do not have excellent cleavage properties. In addition the measurements should be more immune from sample ageing on surfaces which are considered to cleave well. This should overcome one of the major limitations of ARPES, enabling cleaner and more trustworthy data which ultimately may answer fundamental questions such as the origin of the pairing interactions in high Tc superconductors. An important component of the activity is the interdisciplinary training of students in the fields of optics, solid state physics, and synchrotron radiation. In addition, the P.I. leads an REU (Research Experience for Undergraduates) program and will continue to include undergraduates in this research.Einstein received his Nobel prize for the photoelectric effect, in which an incident photon (individual packet of light) ejects an electron from a solid. This technique has matured into what is arguably the most powerful probe of the quantum-mechanical state of the electrons within a solid. This individual investigator award supports a project that will apply the technique to study some of the most interesting and potentially useful solids - high temperature superconductors (materials with zero resistance to electric flow) and colossal magnetoresistive oxides (materials which undergo a "colossal" change in their electrical resistance if a magnetic field is applied to the sample). The goal is to understand the basic quantum mechanical interactions in these materials that are responsible for the unique electrical and magnetic properties of the materials. Two novel and powerful sources will be utilized for the generation of the photons to be used in the experiment. One is a new beamline at the Advanced Light Source, Berkeley, which is the nation's preeminent synchrotron radiation facility producing soft X-rays. The other is a laser system, which the PI's research group has built in their laboratory. With this home-built system, the group has made what they believe is the first demonstration of laser-based angle-resolved photoemission spectroscopy. An important component of the activity is the interdisciplinary training of students in the fields of optics, solid state physics, and synchrotron radiation. In addition, the P.I. leads an REU (Research Experience for Undergraduates) program and will continue to include undergraduates in this research.