Theory of relaxation phenomena in glasses and doped semiconductors at low temperatures

Low-temperature relaxation properties of dielectric glass and doped disorde red semiconductors, also called Fermi glasses, are studied. The isomorphism in the description of both types of material is established. In particular , it is proved that the flip-flop relaxation mechanism, which is a characte ristic of dielectric glasses, is also specific for Fermi glasses. The low-t emperatures behavior for the thermal conductivity, electrical conductivity and nuclear relaxation in the glassy systems considered is investigated. Th e relation to experiment is analyzed, which allows us to clarify the key ro le of the flip-flop processes in the formation of the universal properties of disordered dielectrics. This assertion is still a point of much controve rsy. (C) 2000 Elsevier Science B.V. All rights reserved.