Specific heat at low temperatures in quasiplanar molecular crystals: Where do glassy anomalies in minimally disordered crystals come from?
| Autor: | Szewczyk, Daria, Moratalla, Manuel, Chajewski, Grzegorz, Gebbia, Jonathan F., Jeżowski, Andrzej, Krivchikov, Alexander I., Barrio, María, Tamarit, Josep Ll., Ramos, Miguel A. |
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| Rok vydání: | 2024 |
| Předmět: | |
| Zdroj: | Physical Review B 110, 174204 (2024) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1103/PhysRevB.110.174204 |
| Popis: | We present low-temperature specific heat (Cp) measurements of a monoclinic P2_{1}/c crystal formed by quasiplanar molecules of tetrachloro-m-xylene. The dynamic disorder frozen at low-temperature of the asymmetric unit (formed by a half molecule) consists of reorientation around a three-fold-like axis perpendicular to the benzene ring. Such a minimal disorder gives rise to typical glassy anomalies, as a linear in contribution in Cp ascribed to two-level systems and a broad maximum around 6.6 K in Cp/T^3 (the boson peak). We discuss these results in the framework of other quasiplanar molecular crystals with different accountable number of in-plane molecular orientations We find that the density of two-level systems does not correlate with the degree of orientational disorder. Rather, it is the molecular asymmetry that seems to play a relevant role in the thermal anomalies. Furthermore, we discuss the suggested correlation between the boson peak and Debye temperatures. We find that a linear correlation between the boson peak and Debye temperatures holds for many -- but not all -- structural glasses and strikingly holds even better for some disordered crystals, including our studied quasiplanar molecular crystals. Comment: 27 pages, 11 figures, 4 tables |
| Databáze: | arXiv |
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