Cryogenic tunneling losses at microwave frequencies in polymeric dielectrics

Abstract

A highly sensitive measurement method using superconducting microwave resonators was employed to study the dielectric loss mechanisms in polymeric materials (PE and PTFE) between 0.1…10 GHz and 2…4 K. The measured temperature and frequency dependence of the loss tangent proves for the first time the existence of one-phonon tunneling processes in a frequency-temperature range which has been fairly inaccessible for experiments until now. The loss may be attributed to strong motions of sidegroup dipoles, backbone sections, or electrically active impurities even at temperatures far below the glass point.