Angle-Resolved Photoemission Experiments of Correlated Electronic Systems

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Technical: High resolution angle resolved photoemission (ARPES) will be used to study the electronic structure of correlated electron systems, particularly colossal magnetoresistive (CMR) oxides. Past work from this program has produced the largest body of published electronic structure information on CMR oxides which now allows us to open the next level of even deeper questions, many of which transcend far beyond the manganites. Also setting this work apart are very important and powerful collaborations with multiple x-ray and neutron scattering groups, an optics group, and a theory group for calculation of the band structure, correlation effects, and photoemission matrix elements. The program will principally utilize high resolution photoemission beamlines at the Advanced Light Source, Berkeley. 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.Non-Technical: 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. We will apply this technique to study a particularly interesting and potentially useful effect, colossal magnetoresistance or CMR. In CMR materials, the application of a magnetic field induces "colossal" (up to 11 orders of magnitude) changes in electrical resistance which may be many. Our goal is to understand the basic quantum mechanical interactions in these materials that is responsible for their unique electrical and magnetic properties. The program will principally utilize high resolution photoemission beamlines at the Advanced Light Source, Berkeley, which is the nation's preeminent synchrotron radiation facility producing soft X-rays. 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.