Evidence for undamped waves on ohmic materials

In this work, we present a historical review of the developments of the field of impedance spectroscopy technique, pointing out some recent advances toward accuracy improvements and new applications. The requirements for physically realizable impedances, which are provided by Linear System Theory, are summarized and discussed for a set of measured data. Some metrology issues are also mentioned and referenced. Original studies concerning a never before observed region of the impedance spectra of conducting materials are also presented. It was found that the real part of passive circuits may attain negative values. A first-principle model that permitted us to perform calculations that forecast this so far concealed part of the impedance spectra is presented. On these footings, it seems that a specific propagation mode of electromagnetic fields in matter is the cause for this unusual spectral response. Our predictions were confirmed by a set of carefully conducted experiments. Calculations and experiments were performed on metallic and carbon-made spires and coils, of specific geometry, in the MHz range. Our data demonstrate that, in fact, the impedance of a carefully engineered passive circuit may assume phase angle values belonging to the full trigonometric circle [−π, π].