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arXiv 2302.14441cond-mat.mtrl-scicond-mat.dis-nn
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准晶中由超原子涨落引发的原子扩散

Atomic diffusion due to hyperatomic fluctuation for quasicrystals

Yuki Nagai, Yutaka Iwasaki, Koichi Kitahara, Yoshiki Takagiwa, Kaoru Kimura, Motoyuki Shiga

AI总结:

针对准晶高温热容反常的理论研究空白,该研究通过Al-Pd-Ru准晶的实验与分子模拟,发现铝原子扩散对应六维超原子涨落,揭示热容反常源于超原子涨落的额外自由度。

摘要:

准晶是一种有序但非周期性的结构,可理解为高维周期性结构的投影。准晶的部分物理性质与传统固体不同,其高温下热容的反常升高现象作为准晶隐含高维特性的表现,已被探讨了二十余年。该现象的一个合理候选起源是相位子(phason),它具有源自高维晶格额外自由度的激发模式,但大多数关于相位子的理论研究都采用了玩具模型,由于计算复杂度极高,目前尚未针对真实准晶或其近似相开展热容相关的理论研究。为填补实验与理论之间的这一空白,我们对同一种材料——Al-Pd-Ru准晶及其近似相——开展了实验与分子模拟研究。结果表明,高温下铝原子以类不连续跳跃的方式扩散,且铝的扩散路径可通过对应六维空间中超原子涨落的跳跃来解释。研究得出结论:准晶的热容反常源于超原子涨落带来的额外自由度,这类涨落在扩散型Nambu-Goldstone模中发挥作用。

英文摘要:

A quasicrystal is an ordered but non-periodic structure understood as a projection from a higher dimensional periodic structure. Some physical properties of quasicrystals are different from those of conventional solids. An anomalous increase in heat capacity at high temperatures has been discussed for over two decades as a manifestation of a hidden high dimensionality of quasicrystals. A plausible candidate for this origin has been phason, which has excitation modes originating from additional degrees of freedom in the higher-dimensional lattice. However, most theoretical studies on phasons have used toy models. A theoretical study of the heat capacity of realistic quasicrystals or their approximants has yet to be conducted because of the huge computational complexity. To bridge this gap between experiment and theory, we show experiments and molecular simulations on the same material, an Al--Pd--Ru quasicrystal, and its approximants. We show that at high temperatures, aluminum atoms diffuse with discontinuous-like jumps, and the diffusion paths of the aluminum can be understood in terms of jumps corresponding to hyperatomic fluctuations in six-dimensional space. It is concluded that the anomaly in the heat capacity of quasicrystals arises from extra degrees of freedom due to hyperatomic fluctuations that play a role in diffusive Nambu--Goldstone modes.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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