Glass-like, low-energy excitations in neutron-irradiated quartz

The specific heat and thermal conductivity of neutron-irradiated crystalline quartz have been measured for temperatures approx. 0.1 to 5 K. Four types of low-energy excitations are observed in the irradiated samples, two of which can be removed selectively by heat treatment. One set of remaining excitations gives rise to low-temperature thermal behavior characteristic of glassy (amorphous) solids. The density of these glass-like excitations can be 50% the density observed in vitreous silica, yet the sample still retain long-range atomic order. In a less-irradiated sample, glass-like excitations may be present with a density only approx. 2.5% that observed in vitreous silica and possess a similar broad energy spectrum over 0.1 to 1 K