SRC Quantum Lunch
Tom Miller, University of Illinois at Urbana—Champaign
"Development of a Microfocus Beamline for Angle—Resolved Photoemission at the SRC"
About the Research:
A microfocus photoemission beamline is being developed at the Synchrotron Radiation Center (SRC) for advanced materials research and education. Materials of current research interest, including complex oxides, high temperature superconductors, ferroelectrics, colossal magnetoresistive materials, multiferroics, f-electron materials, etc., often develop domains, patterns, or inhomogeneities due to spontaneous phase separation, inhomogeneous dopant or defect distribution, and non-unique surface/interface chemical compositions or terminating atomic planes. These effects can give rise to novel phenomena and properties that are key to the functionality of the materials. In addition, with real samples one commonly encounters uneven cleavages, atomic steps, crystal facets, etc.
These naturally occurring as well as artificially tailored structures are of great scientific importance, and a basic understanding of the electronic effects in such systems is crucial for technological advances in many areas. Angle-resolved photoemission is the most general tool for band structure or spectral function mapping. However, work to date is mostly limited by the probe size, and thus spectral features specific to microscopic regions and spatial modulations are hard to unravel. For example, cleaving may naturally expose different crystal planes, and the area covered by the incident photon beam may then consist of a collection of small domains with different photoemission spectra. The result is an average which obscures the true nature of the material. This is a serious obstacle to discoveries and fundamental understandings.
The new system will involve modifications to PGM-B undulator beamline at SRC and to one of the Scienta photoemission chambers to accomodate new microfocusing optical systems based on coated Schwarzschild mirrors, and will enable high-resolution angle-resolved photoemission at the micron and sub-micron scales. It will have broad scientific impact on numerous material systems of general interest, and the number of users that can potentially benefit from the capabilities of the new instrument will be very large.