Optical conductivity of CuO2 infinite-layer films

The infrared conductivity of CaCuO2, SrCuO2-y, and Sr0.85Nd0.15CuO2 infinite-layer films is obtained from reflectivity measurements by taking into account the substrate contribution. SrCuO2-y and Sr0.85Nd0.15CuO2 exhibit extra-phonon modes and structured bands in the midinfrared, not found in stoichiometric CaCuO2. These features mirror those observed in the perovskitic cuprates, thus showing that the polaronic properties of High-T-c superconductors are intrinsic to the CuO2 planes.