Verifying the Drude response

By now more than 100 years passed since Paul Drude suggested his highly acclaimed model of electronic transport. In the form advanced by A. Sommerfeld. the Drude model is still heavily utilized to describe. for instance, the optical properties of metals. Surprisingly. the key prediction of the Drude model. the frequency dependence of the complex conductivity with its pronounced roll-off was directly observed in an experiment only very recently. Here we present direct and independent measurements of both the real and imaginary parts of the metallic conductivity in a large range of frequency around the scattering rate. (C) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.