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Encouraging discussions with A.J. Leggett are gratefully acknowledged. This work has been partially supported by the Spanish Ministry of Economy through project FIS2017-84330-R, as well as by the Autonomous Community of Madrid through programme NANOFRONTMAGCM (S2013/MIT-2850).

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Residual entropy in the zero-temperature limit of toluene glass

Publicado en:LOW TEMPERATURE PHYSICS. 45 (3): 331-336 - 2019-03-01 45(3), DOI: 10.1063/1.5090091

Autores: Moratalla, M; Bejarano, P; Castilla, J M; Ramos, M A

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Resumen

The specific heat C-p of toluene, doped with 2 mol% ethanol to avoid rapid crystallization, has been measured in both glass and crystal states, and with special accuracy at low temperatures in the range 1.8-20 K using the thermal relaxation method. By making use of the complementary C-p curves measured in the reference crystal state, we have been able to obtain the entropy curve of the glass and eventually the residual entropy of toluene glass in the zero-temperature limit, that is found to be 5.1 J/(K.mol). This value is clearly lower than others pre-viously reported in the literature, which lack the knowledge of the particular specific-heat behavior of glasses at low temperatures and hence overestimated the glass residual entropy at zero temperature. In addition, we have studied in detail such low-temperature glassy anomalies in the case of toluene, extending and improving pre-vious measurements. The surprising depletion previously reported of tunneling two-level systems in toluene glass has been confirmed, though this fact coexists with the presence of a broad peak typical of glasses (the so-called boson peak) in C-p/T-3 at 4.5 K. For the toluene crystal, the expected cubic Debye behavior has been found at lower temperatures. Published under license by AIP Publishing.

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