Abstract
The in-plane optical properties of two crystals of the bilayer cuprate one with excess Ca and and the other with Sr and were investigated over the frequency range of 45– The optical conductivity has been derived from Kramers-Kronig transformation. Each crystal exhibits a peak at around which corresponds to the charge-transfer (CT) excitation of the parent insulator. With increasing carrier density, spectral weight shifts from the CT excitation to the low- region. For the superconducting sample the optical conductivity displays a peak in the far-infrared region, which shifts toward zero frequency with decreasing temperature. The temperature-dependent behavior favors a dynamical localization picture. A “pseudogap” feature is observed in the low-frequency reflectance and the scattering rate spectra. Both the energy scale and the temperature dependence of the pseudogap are similar to other bilayer cuprates.
- Received 8 November 2002
DOI:https://doi.org/10.1103/PhysRevB.67.134526
©2003 American Physical Society