Hi, In deriving a complex wave vector for waves in media, an equation D = ε E is typically used. Later though, it is common to relate D and E through a complex ε which is generally written as εcomplex = ε + 4 pi i σ / ω. It seems a contradiction to insert one relationship into the Maxwell equations and then explain how really it's another, where a complex epsilon allows for a phase shift between D and E. I'm also confused whether the σ here is necessarily complex; in the constituitive relation used to derive it, we had j = σ E and from the Dressel Electrodynamics of Solids book and the Wooten online optical solid state book he identifies σ as real. See, for example, http://web.mit.edu/course/6/6.732/www/6.732-pt2.pdf pages 2-3. Thanks!