Phonon–roton-like elementary excitations and low-temperature behaviour of non-crystalline solids

Abstract

The low-temperature behaviour of the specific heat of a glassy sample is explained in analogy to what is done in the physics of superfluid helium. The low-temperature excitation spectra of the system is assumed as being formed by two ideal gases of quasiparticles. One of them is a phonon gas, leading to the Debye contribution, and the other one is an ideal gas of another bosonic quasiparticle, whose dispersion relation is similar to the one proposed for liquid helium.

Acknowledgements

This work was partially financed by the Brazilian Agencies Capes, CNPq and Fundação Araucária.

Notes

†In the case of superfluid helium, only the phonon gas is bosonic; the roton gas, in the He II temperature range, is treated by means of the Maxwell-Boltzmann statistics.