Tunneling states and the low-temperature thermal expansion of glasses

Abstract

A recent theoretical model, based on tunneling states, for the heat capacity and thermal conductivity of amorphous solids below 1 K is extended to include thermal expansion. The calculated Grüneisen constant γ is sensitive to the details of the tunneling states, but the model provides an explanation for the large negative values of γ observed in vitreous silica below 4 K.