The optical spectrum of reduced-Tc GdBa2Cu3O7-δ has been measured for polarizations parallel and perpendicular to the ab plane. The sample was an oxygen-deficient single crystal with a large face containing the c axis. The polarized reflectance from this face was measured from 20-300 K in the spectral region from 30-3000 cm-1, with 300 K data to 30000 cm-1. Kramers-Kronig analysis was used to determine the spectral dependence of the ab and the c components of the dielectric tensor. The optical properties are strongly anisotropic. The ab-plane response resembles that of other reduced-Tc materials whereas the c axis, in contrast, shows only the presence of several phonons. There is a complete absence of charge carrier response along c above and below Tc. This observation allows us to set an upper limit to the free-carrier spectral weight for transport perpendicular to the CuO2 planes.
ASJC Scopus subject areas
- Condensed Matter Physics