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Low-temperature specific heat and thermal conductivity of silica aerogels

1991; American Physical Society; Volume: 66; Issue: 8 Linguagem: Inglês

10.1103/physrevlett.66.1070

1092-0145

Tycho Sleator, Angelo Bernasconi, Dorthe Posselt, Jørgen Kjems, H. R. Ott,

Material Dynamics and Properties

Specific-heat and thermal-conductivity measurements were made on a series of base-catalyzed silica aerogels at temperatures between 0.05 and 20 K. Evidence for a crossover between regimes of characteristically different excitations was observed. The data analysis indicates a ``bump'' in the density of vibrational states g(\ensuremath{\omega}) at the crossover frequency from phonon to fracton behavior.