It is commonly believed that electromagnetic waves cannot propagate in lossy conductive media and that they quickly decay inside such media over short length scales of the order of the so-called skin depth. Here we prove that this common belief is incorrect if the conductive medium is stratified. We demonstrate that electromagnetic waves in stratified lossy conductive media may have propagating character, and that the propagation length of such waves may be considerably larger than the skin depth in homogeneous media. Our findings have broad implications in many fields of science and engineering. They enable radio communication and imaging in such strongly lossy conductive media as seawater, various soils, plasma and biological tissues. They also enable novel electromagnetic metamaterial designs by mediating the effect of losses on electromagnetic signal propagation in metamaterials. Our results demonstrate a new class of inherently non-Hermitian electromagnetic media with high dissipation, no gain, and no PT-symmetry, which nevertheless have almost real eigenvalue spectrum.
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