Specific heat of thin phonon cavities at low temperature : Very high values revealed by zeptojoule calorimetry
Tavakoli, A., Lulla, K. J., Puurtinen, T., Maasilta, I., Collin, E., Saminadayar, L., & Bourgeois, O. (2022). Specific heat of thin phonon cavities at low temperature : Very high values revealed by zeptojoule calorimetry. Physical Review B, 105(22), Article 224313. https://doi.org/10.1103/PhysRevB.105.224313
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Physical Review BAuthors
Date
2022Copyright
© 2022 American Physical Society
The specific heat of phonon cavities is investigated in order to analyze the effect of phonon confinement on thermodynamic properties. The specific heat of freestanding very thin SiN membranes in the low-dimensional limit is measured down to very low temperatures (from 6 K to 50 mK). In the whole temperature range, we measured an excess specific heat orders of magnitude bigger than the typical value observed in amorphous solids. Below 1 K, a crossover in cp to a lower power law is seen, and the value of the specific heat of thinner membranes becomes larger than that of thicker ones demonstrating a significant contribution coming from the surface. We show that this high value of the specific heat cannot be explained by the sole contribution of two-dimensional phonon modes (Lamb waves). The excess specific heat, being thickness dependent, could come from tunneling two-level systems that form in low-density regions of amorphous solids located on the surfaces. We also show that the specific heat is strongly tuned by the internal stress of the membrane by orders of magnitude, giving high values, making low-stress SiN very efficient for energy storage at very low temperature.
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American Physical Society (APS)ISSN Search the Publication Forum
2469-9950Publication in research information system
https://converis.jyu.fi/converis/portal/detail/Publication/150945413
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Research Council of FinlandFunding program(s)
Academy Project, AoFAdditional information about funding
The research leading to these results has received funding from the European Union's Horizon 2020 research and innovation program, under Grant Agreement No. 824109; the European Microkelvin Platform (EMP); the EU project MERGING, Grant No. 309150; and ERC CoG Grant ULT-NEMS No. 647917. The authors also acknowledge the financial support from the ANR project QNM, Grant No. 040401. T.P. and I.M. acknowledge the financial support from Academy of Finland Project No. 341823. ...License
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