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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 the additional atomic rearrangements introduced by the quasiperiodic order, which can be understood in terms of shifting a 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 associated atomic rearrangements of the phason degrees of freedom. It is concluded that the anomaly in the heat capacity of quasicrystals arises from the hyperatomic fluctuations that play a role in diffusive Nambu–Goldstone modes.

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  © 2024 American Physical Society　　

Keyword: Quasicrystal, specific heat, machine-learning molecular dynamics, phason

Date published: 2024-05-10

Publisher: American Physical Society (APS)

Journal:

• Physical Review Letters (ISSN: 10797114) vol. 132 issue. 19 196301

Funding:

• Japan Society for the Promotion of Science 18K11345
• Japan Society for the Promotion of Science 20H05278
• Japan Society for the Promotion of Science 22H04602
• Japan Society for the Promotion of Science 22K03539
• Japan Society for the Promotion of Science 19H05818
• Japan Society for the Promotion of Science 19H05821
• Japan Society for the Promotion of Science 19J21779
• Japan Society for the Promotion of Science 18H05519
• Japan Society for the Promotion of Science 21H01603

Manuscript type: Author's version (Accepted manuscript)

MDR DOI: https://doi.org/10.48505/nims.4652

First published URL: https://doi.org/10.1103/physrevlett.132.196301

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Updated at: 2024-08-19 12:30:16 +0900

Published on MDR: 2024-08-19 12:30:16 +0900