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arXiv 0912.4647cond-mat.stat-mech
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玻璃态对六角晶系$^4$ He固体heat capacity的贡献

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

Jung-Jung Su, Matthias J. Graf, Alexander V. Balatsky

摘要:

我们模型的低温比热固体$^4$他在六方密堆积结构调用两个级别的隧道状态除了通常的德拜晶体的声子贡献的温度远低于德拜温度,$T < Θ_D/50$。通过在二能级隧穿态密度中引入截止能,我们可以描述在固态六方晶系$^4$ He中观测到的过剩比热,以及比热中的低温线性项。协议被发现与最近的测量的比热和压力的温度行为。这些结果表明,存在一个非常小的分数,在百万分之一(ppm)的水平,在固体$^4$ He的二能级隧穿系统,无论超固体的存在。

英文摘要:

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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