Abstract

Measurements of the IR properties of the new oxide superconductors are being made both to characterize the electrodynamic properties in the normal state and to identify the energy gap and possible electron coupling mechanisms in the superconducting state. Using optical and IR Fourier transform spectroscopic techniques, reflectivity and direct absorption measurements have been made on bulk sintered materials, thin films, and single crystals of these high T_c materials over an extended frequency interval. Kramers-Kronig and mode analysis of these data give the real and imaginary parts of the frequency-dependent conductivity, a quantity which can be compared directly with theoretical predictions. For the sintered materials the anisotropic grain effects must be unfolded from the conductivity before the energy gap can be identified. Comparing all these data for the superconducting state with the predictions of BCS theory shows that absorption occurs at frequencies below the apparent electromagnetic energy gap and that the effective gap position depends on the sample texture.

© 1988 Optical Society of America