Raman Scattering Studies on Superconducting YBa₂Cu₃O_7−x, Semiconducting YBa₂Cu₃O_6+x, and Possible Impurity Phases

ABSTRACTA Raman spectroscopie investigation of specimens of superconducting YBa2Cu3O7−x and semiconducting YBa2Cu3O6+x indicates that in the range 100 to 700 cm-1, the characteristic lines of the superconductor at 13 K, are at 150, 338, 441, 507, 590, and 644 cm-1. Comparison of the Ranan spectra of the superconductor and the semiconductor indicates a mode stiffening of the pair at 338 and 441 cm-1, hut a mode softening of the pair at 507 and 590 cm-1. A factor group analysis leads to a tentative assignment of the Raman and infrared allowed modes. At temperatures 12K &lt; T &lt; 180K the Raman spectra of the superconductor indicate that the phonon mode at 338 cm-1 has an anomalous temperature dependence below the superconducting critical temperature (Tc).</jats:p