发表机构
Univ. Grenoble Alpes; CNRS; CEA（格勒诺布尔阿尔卑斯大学; 法国国家科学研究中心; 法国原子能和替代能源委员会）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究通过大规模分子动力学模拟，揭示了弱非谐FPUT链中反常热输运由对角声子模式关联控制，并推导出热导率随系统尺寸的标度律，表明弱非谐性仅推迟而非改变声子主导输运的渐近机制。
AI 中文摘要
我们利用大规模平衡分子动力学模拟，研究了弱非谐区域中一维β-Fermi-Pasta-Ulam-Tsingou链的反常热输运。通过将热流分解为声子模式贡献，我们证明其长时间自相关由对角模式关联控制，其衰减由相应的声子阻尼率定量决定。外推到热力学极限得到Γ_k ∝ (βT)^{4/3} k^{5/3}，并带有次主导的k^2修正。后者产生一个扩展的前渐近区域，C(t) ~ t^{-4/5}，之后达到渐近衰减C(t) ~ t^{-3/5}，导致κ(N) ~ N^{2/5} + O(N^{1/5})。在弱非谐情况下，非对角模式关联持续到特征时间τ_od ~ (βT)^{-2}，而需要越来越大的系统来分辨长波声子贡献。因此，弱非谐性不会引入不同的渐近输运机制，而是将声子主导区域的起始转移到更长的时间和更大的长度尺度。
英文摘要
We investigate anomalous heat transport in the one-dimensional $β$-Fermi--Pasta--Ulam--Tsingou chain in the weakly anharmonic regime using large-scale equilibrium molecular dynamics. By resolving the heat current into phonon-mode contributions, we show that its long-time autocorrelation is controlled by diagonal mode correlations, whose decay is quantitatively determined by the corresponding phonon damping rates. Extrapolation to the thermodynamic limit gives $Γ_k \propto (βT)^{4/3} k^{5/3}$, with a subleading $k^2$ correction. The latter produces an extended pre-asymptotic regime, $C(t) \sim t^{-4/5}$, before the asymptotic decay $C(t) \sim t^{-3/5}$ is reached, leading to $κ(N) \sim N^{2/5} + O(N^{1/5})$. At weak anharmonicity, off-diagonal mode correlations persist up to a characteristic time $τ_{\mathrm{od}} \sim (βT)^{-2}$, while increasingly large systems are required to resolve the long-wavelength phonon contribution. Weak anharmonicity therefore does not introduce a distinct asymptotic transport mechanism, but shifts the onset of the phonon-dominated regime to progressively longer times and larger length scales.
