Phonon frequency spectrum of the HTSC EuBa 2Cu 3O 7

Abstract

The assignments of spectral features to specify lattice vibrations are an important step to understand their role of superconductivity. Raman and infrared studies have contributed significantly to the explication of high T c superconductor mechanics. Although many reports of superconductivity for rare earth atoms have appeared, a systematic investigation for the whole rare earth family is scarce. Cardona and others studied the Raman infrared spectra of the superconducting cuprate perovskites and reported the origin of phonon softening and the systematic variation of phonon frequencies with ionic radius. In the present work, normal coordinate calculations have been employed to study the vibrational analysis of metal oxides. These calculations using infrared and Raman details have allowed a detailed assignment of the vibrational features of the superconducting system. For the basic understanding of physical properties such as thermal, elastic, dielectric and infrared, etc., it is indispensable to have knowledge of the phonon frequency spectrum which can also be achieved by means of theoretical models of lattice dynamics. A three-body shell model (TSM) which takes into account of many body interactions is applied to study the lattice dynamics of the high T c oxide EuBa 2Cu 3O 7. The phonon frequencies at the zone centre of Brillouin zone which are of interest for the interpretation of the infrared and Raman spectrum are presented and the vibrational assignments are discussed. The calculations yield not only the phonon frequencies at the zone centre but also throughout the Brillouin zone. Thus, lattice dynamical calculations and normal coordinate analysis give same phonon frequencies for high T c oxide EuBa 2Cu 3O 7 through solid state physics and spectroscopy.