Do tunneling states and boson peak persist or disappear in extremely stabilized glasses?

• Published in: Физика низких температур
• Date: 2015
• Main Authors: Ramos, M.A., Pérez-Castañeda, T., Jiménez-Riobóo, R.J., Rodríguez-Tinoco, C., Rodríguez-Viejo, J.
• Format: Article
• Language: English
• Published: Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України 2015
• Subjects: 10th International Conference on Cryocrystals and Quantum Crystals
• Online Access: https://nasplib.isofts.kiev.ua/handle/123456789/127824
• Journal Title: Digital Library of Periodicals of National Academy of Sciences of Ukraine
• Cite this: Do tunneling states and boson peak persist or disappear in extremely stabilized glasses?
 / M.A. Ramos, T. Pérez-Castañeda, R.J. Jiménez-Riobóo, C. Rodríguez-Tinoco, J. Rodríguez-Viejo // Физика низких температур. — 2015. — Т. 41, № 6. — С. 533-540. — Бібліогр.: 45 назв. — англ.

We review and concurrently discuss two recent works conducted by us, which apparently give opposite results.
 Specifically, we have investigated how extreme thermal histories in glasses can affect their universal properties
 at low temperatures, by studying: (i) amber, the fossilized natural resin, which is a glass which has experienced
 a hyperaging process for about one hundred million years; and (ii) ultrastable thin-film glasses of
 indomethacin. Specific heat Cp measurements in the temperature range 0.07 K < T < 30 K showed that the
 amount of two-level systems, assessed from the linear term at the lowest temperatures, was exactly the same for
 the pristine hyperaged amber glass as for the subsequently rejuvenated samples, whereas just a modest increase
 of the boson-peak height (in Cp/T³) with increasing rejuvenation was observed, related to a corresponding increase
 of the Debye coefficient. On the other hand, we have observed an unexpected suppression of the two-level
 systems in the ultrastable glass of indomethacin, whereas conventionally prepared thin films of the same material
 exhibit the usual linear term in the specific heat below 1 K ascribed to these universal two-level systems in
 glasses. By comparing both highly-stable kinds of glass, we conclude that the disappearance of the tunneling
 two-level systems in ultrastable thin films of indomethacin may be due to the quasi-2D and anisotropic behavior
 of this glass, what could support the idea of a phonon-mediated interaction between two-level systems.