Low-energy dynamics in disordered materials

Heat transport phenomena as the thermal conductivity or heat capacity in structurally disordered materials are different from those in crystal materials in low temperature region. These universal thermophysical properties in an atomic scale are directly related to the low-energy excitations, called Boson Peak, observed by neutron inelastic scattering and Raman scattering measurements. In addition, some results of the vibrational density of states obtained by neutron inelastic scattering measurement suggest the validity of two-level-system model which is widely accepted theoretical model of these universal thermophysical properties. (author)