Memory-effect in glasses at low temperatures

The dielectric constant of amorphous solids at low temperatures is governed by the dynamics of tunneling systems, small groups of atoms which tunnel between quasi equivalent potential minima. Recent experiments showed that at temperatures below 20 mK various glasses exhibit memory for a previously applied electric bias field. A first sweep of an electric bias field may prepare resonant pairs of tunneling systems, which are temporarily formed during the sweep, in metastable states. In subsequent sweeps the same resonant pairs thus significantly contribute to the dielectric constant, leading to a higher dielectric constant. We investigate the dynamics of resonant pairs during a bias field sweep yielding a qualitative explanation of the memory effect.