Dynamic conductivity and the coherence peak in the submillimeter spectra of superconducting NbN films

Abstract A new technique is developed for measurement of electrodynamic parameters of superconducting films in the submillimeter wavelength range. In the frequency range 5–39 cm −1 at temperatures 5–300 K, the first detailed measurements of the temperature and frequency dependences of dynamic conductivity and dielectric permittivity of superconducting NbN films are performed. A coherence peak is discovered in the temperature dependence of dynamic conductivity of NbN films.