Photoemission Experiments of Correlated Electron Systems

高分辨率角分辨光电发射（ARPES）将用于研究相关电子系统的电子结构，特别是巨磁阻（CMR）氧化物和高Tc超导体。该项目将利用位于先进光源光束线12的一个新的高分辨率终端站，以及位于科罗拉多州的一个独特的基于激光的光电发射系统。这两种设置都带来了出色的光谱分辨率，与标准ARPES实验相比，激光还允许降低表面灵敏度。这种降低的表面灵敏度可以使ARPES实验扩展到更广泛的材料，如高Tc超导体YBa(2)Cu(3)O(7)，这些材料没有优异的解理性能。此外，在被认为劈裂良好的表面上，测量应该更不受样品老化的影响。这将克服ARPES的一个主要限制，使数据更清晰、更可信，最终可能回答诸如高Tc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在光学、固体物理和同步辐射领域对学生进行跨学科训练。此外，P.I.领导一个REU（本科生研究经验）项目，并将继续包括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）从固体中射出一个电子。这项技术已经成熟，可以说是固体中电子量子力学状态最强大的探测。这项个人研究者奖将支持一个项目，该项目将应用该技术研究一些最有趣和潜在有用的固体——高温超导体（对电流无电阻的材料）和巨大磁阻氧化物（如果对样品施加磁场，其电阻会发生“巨大”变化的材料）。我们的目标是了解这些材料中基本的量子力学相互作用，这些相互作用是材料独特的电和磁特性的原因。两种新型的强力光源将用于产生实验中使用的光子。其中之一是位于伯克利的先进光源的新光束线，这是美国最杰出的同步辐射设备，可以产生软x射线。另一个是激光系统，这是PI的研究小组在他们的实验室里建造的。有了这个自制的系统，该小组已经完成了他们认为是基于激光的角分辨光谱学的第一次演示。该活动的一个重要组成部分是在光学、固体物理和同步辐射领域对学生进行跨学科训练。此外，P.I.领导一个REU（本科生研究经验）项目，并将继续包括本科生参与这项研究。

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.