Phonons inCaCuO2

Abstract

${\mathrm{CaCuO}}_2$ is the infinite number of Cu-O planes limit of most of the high-temperature superconductors. From infrared reflectivity of ceramic (${\mathrm{Ca}}_{0.86}$ ${\mathrm{Sr}}_{0.14}$)${\mathrm{CuO}}_2$, we have measured all five of the group-theoretically allowed phonons. Also, group theory predicts no Raman-allowed phonons, in agreement with our observations. We compare the observed phonons with those reported in other high-temperature superconductors and, in particular, with ${\mathrm{Nd}}_2$ ${\mathrm{CuO}}_4$ (T’ structure) because of the similar Cu-O plane structural element.