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arXiv · 0912.4647

A glassy contribution to the heat capacity of hcp $^4$He solids

Jung-Jung Su·Matthias J. Graf·Alexander V. Balatsky
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Abstract

We model the low-temperature specific heat of solid $^4$He in the hexagonal closed packed structure by invoking two-level tunneling states in addition to the usual phonon contribution of a Debye crystal for temperatures far below the Debye temperature, $T < Θ_D/50$. By introducing a cutoff energy in the two-level tunneling density of states, we can describe the excess specific heat observed in solid hcp $^4$He, as well as the low-temperature linear term in the specific heat. Agreement is found with recent measurements of the temperature behavior of both specific heat and pressure. These results suggest the presence of a very small fraction, at the parts-per-million (ppm) level, of two-level tunneling systems in solid $^4$He, irrespective of the existence of supersolidity.

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Jung-Jung Su, Matthias J. Graf, Alexander V. Balatsky. 2010-01-27. A glassy contribution to the heat capacity of hcp $^4$He solids. https://doi.org/10.1007/s10909-010-0163-x

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