Optical phonons of superconducting infinite-layer compounds Sr0.9Ln0.1CuO2 (Ln=La and Sm)

Authors identified the optical phonon modes of high-quality superconducting infinite-layer compounds Sr0.9Ln0.1CuO2 (Ln=La and Sm, Tc=43 K for both) from their ir reflectivity spectra obtained with FTIR. The La-doped compound exhibited only four (2A2u+2Eu) out of the five (2A2u+3Eu) ir-active phonon modes predicted by a group theoretical analysis, with one Eu mode screened by free carriers. The Sm-doped compound exhibited all five modes. Authors propose the displacement pattern for each mode based on lattice dynamics calculations and through comparison with the phonon modes of other single-layer high-Tc cuprates. 17 refs.