Optical Reflectivity of Single Crystals of YBa2Cu3O7-δ and ErBa2Cu3O7-δ

Abstract
Optical reflectivity in the a b-plane of single crystals of YBa2Cu3O7-δ and ErBa2Cu3O7-δ has been observed at room temperature in the energy region from 0.5 to 5.6 eV. The reflectivity is isotropic in the a b-plane around the Drude edge at 1.5 eV. In the low-energy region below the edge, it is explained well by the Drude formula for the free carriers with an extremely short relaxation time of about 4×10-16 s.