KRAMERS–KRONIGRELATIONS ANDRESPONSE FUNCTIONS
In this appendix we shall derive the Kramers–Kronig relations. This requires an excursion into the complex frequency plane and Cauchy’s integral theorem; readers unfamiliar with complex analysis can skip Section A6.1 without loss of continuity. We shall then derive two common models for the optical response of semiconductors.
A6.1 Derivation of the Kramers–Kronig Relations
The complex conductivity ...