Nonlinear dielectric response of glasses at low temperature

Abstract

We have measured the dielectric response of amorphous insulators in the audio frequency range at temperatures between 500 μK and 400 mK. We compare the measured superlinear behavior with a model incorporating higher order terms at low frequencies. Temperature independent dielectric response at low fields and low temperatures has also been observed which may indicate a low energy cutoff in the two-level system distribution of order 1 mK in some materials. We also find anomalously high sensitivity of the dielectric response to rf noise.