Additional microwave modes in systems with conductivity of metals and superconductors

Semiclassical model, which takes into consideration the spatial dispersion effects in conductivity and permittivity, demonstrates the possible appearance of additional waves in conducting media, which are known to exist in transparent dielectrics near a narrow absorption band. The dispersion law of additional waves for modelling media (one-dimensional conductance) with parameters of Cu and Nb is obtained, which predicts the novel phenomenon-the possibility for additional microwave modes to propagate in metals with low enough attenuation at cryogenic temperatures.