Abstract
We have measured the -axis optical response of a large, high-quality single crystal of Cu between 30 and 700 in the 10-300 K temperature range with a far-infrared Fourier ellipsometer. Since ellipsometry provides both amplitude and phase information, we directly obtain the complex dielectric function, thereby avoiding the errors introduced by the Kramers-Kronig transformation or the reference determination. A purely algebraic treatment of our data within the two-fluid Gorter-Casimir model reveals no indication of a reduction of the normal carrier scattering rate below . We obtain and a plasma frequency for the superconducting carriers of . Thus, assuming a weak-coupling BCS gap ( , with K) we conclude that the -axis optical response of Cu can neither be modeled within the clean nor with the dirty limit.
- Received 30 June 1995
DOI:https://doi.org/10.1103/PhysRevB.53.9353
©1996 American Physical Society