Comparative Studies Between Lattice Dynamical Study and Normal Coordinate Analysis of HTSC EuBa2Cu3O6

Abstract

It is generally believed, that is needed to sign post the way to the development of materials with high critical temperature, even to room temperature and above, is the formulation of a proper theoretical understanding of superconductivity in these materials. Many experimental studies suggest an intimate relationship between phonons, and the superconducting transition in the high Tc oxides.For example, Raman frequencies and line widths, elastic constants and thermal conductivity all show changes around Tc. Nevertheless, there is not a well- developed theory to explain how the phonons are related to Tc.. In conventional superconductors, the role of phonons is well established. However, in high Tc superconductors, the role played by phonons is controversial. Even if they do not mediate the pairing mechanism, they are likely to play an important subsidiary role. Hence there is much interest in the phonon structure of these materials. The normal state and superconducting properties are believed to arise from the strongly correlated motion of the electronic charge carries (electrons or holes) in the CuO2 planes that essentially define the layered cuprate HTSC. The other cations and oxygen atom in the structure provides structural stability and control the number of charge carries in the CuO2 planes. The Raman spectroscopy of HTSC explains that the role played by the phonons in the mechanism of superconductivity in the perovskite family of superconductors is not fully understood although a large series of experimental results has shown considerable coupling of some phonons to electronic excitation in these systems. Optical spectroscopy and especially Raman and Infrared spectroscopy revealed strong direct influences of the changes in the electronic states to the phonon at the center of the Brillouin.