Raman and Other Optical Properties of Superconductors

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Highly-correlated f-electron metals, especially those that show heavy Fermion behavior, will form the main thrust of this project. Emphasis will be on how the coupling of the f-electron atom to its environment affects optical properties and light scattering. When Raman-active modes are found whose intensity, as with URu2Si2, increases upon the gradual onset of the heavy- Fermion state, a magnetic field will be used to suppress the onset and the effect in the spectra will be observed. Waves in magnetically-ordered states and magnetic excitations will be studied. The strong electronic Gruneisen effect will be exploited by measuring Raman spectra under pressure. The Raman results will be correlated with known elastic constant results and new ones to be obtained using Brillouin scattering. Raman and optical-property measurements will be made on the new high Tc superconductors. Emphasis will be placed on the effects of surface treatment, especially control of oxygen content on the spectra. The role of structural distortions will be elucidated by Raman Brillouin scattering measurements. Correlations will be made with superconducting and structural measurements made by collaborators.