Low Temperature ac Dielectric Response of Glasses to High dc Electric Fields

We report the response of amorphous dielectrics to large dc electric fields E. Upon the rapid application of the field, the ac susceptibility ε^' increases abruptly and then decays logarithmically for t-t₀≈1 to 10⁵ sec. Slow dc field sweeps show a minimum in ε^' at the field present when the sample was cooled from 300 K. If E is held fixed at a different value, a second local minimum in ε^' develops at that field, evident upon subsequent dc field sweeps. We present the temperature, frequency, and amplitude dependences of these related phenomena and discuss possible origins.