PhD THESIS

PhD Thesis in Materials Science, Sapienza University of Rome, Italy

"Infrared Investigation of Oxides Displaying Charge Order and Superconductivity"

PhD awarded on February 14th, 2005.

The thesis presents and extensive infrared and terahertz spectroscopy investigation as a function of temperature on single crystals of the high-critical temperature superconducting cuprate La(2-x)Sr/Ba(x)CuO(4) and of the charge-ordered mobile-ion system Na(x)CoO(2-delta). Both systems display a layered crystal structure and show free-energy competition between the superconducting phase and the charge-ordered, non-superconducting phase. The role of dynamic charge-order correlations in superconductivity and in the determination of the kinetic energy of the electron system is discussed.