Phonon Frequency Spectrum HTSC YbBa2Cu3O7

Abstract

Since the discovery of the high Tc superconductivity by Bednorz and Muller, several workers around the world have studied several systems to reach a really high Tc superconductor. As the strong electron-phonon coupling may be one of the possible origins of the high Tc, a knowledge about the phonon in these materials is essential. In order to investigate phonon spectra, one has to study Raman and infrared spectra of these systems. But there is a little information about the Raman spectra and infrared absorption spectra are available in the literature. Hence, a theoretical evaluation of phonon frequencies of high temperature superconductors assume importance. Due to strong covalent bonding nature in high temperature superconductors, a normal coordinate analysis using Wilson’s FG matrix is applied to evaluate Phonon frequencies. The normal coordinate analysis of optically active lattice vibrations will be useful for the theoretical interpretation of vibrational spectrum at the center of Brillouin zone in high Tc superconductors. Hence, an attempt is made to evaluate all the phonon frequencies of HTSC YbBa2Cu3O7 through normal coordinate analysis. Calculations of lattice dynamics is also performed by use of the modified three body force shell model. The present approach leads to a better understanding of phonon frequency of high Tc superconductor YbBa2Cu3O7 under investigations in the present work. This calculations yield not only the zone center phonon modes but also the stable dispersion curves through out the Brillouin zone. It also supports strong electron-phonon interactions in high Tc superconductors.