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.
