MICROSCOPIC DESCRIPTION OF TUNNELING SYSTEMS IN A STRUCTURAL MODEL GLASS

We present a quantitative method which systematically finds tunneling systems in glasses and hence allows a microscopic check of the standard tunneling model. We apply this method to a two-component model amorphous alloy. The major assumptions of the standard tunneling model are qualitatively verified. Small quantitative differences in the distribution of the tunneling matrix elements explain why the experimental temperature dependence of the specific heat is superlinear and the thermal conductivity is subquadratic. Connections to the soft-potential model and recent strong-coupling models are discussed.