AI 中文总结
该研究提出了一种通过靶向声子激发实现努森数控制热导率响应切换的通用物理框架，揭示了块体与纳米薄膜体系中热导率响应的差异及规律。
AI 中文摘要
靶向声子激发为动态控制热传导提供了一条途径，但目前尚无通用原理可预测频谱选择的非平衡声子群是会增强还是抑制热输运。热导率响应的符号由长平均自由程声子贡献的增加与激发增强的本征散射之间的努森数控制竞争决定。采用第一性原理三声子散射率结合声子跟踪蒙特卡罗模拟，对Ge、Si和3C-SiC从块体晶体到受限纳米薄膜进行研究。在块体体系中，激发增强的散射占主导，热导率主要被抑制；而在纳米薄膜中，低频激发可增加准弹道热输运通道的贡献，从而增强热导率，高频激发则主要起抑制作用。在固定背景温度和激发强度下，这些相反的响应基于归一化目标频率ω_t/ω_D和努森数Kn被组织在频率-努森图谱中，所得框架为超越静态声子工程控制非平衡热输运提供了通用物理基础。
英文摘要
Targeted phonon excitation offers a route to dynamically control heat conduction, yet no general principle predicts whether a spectrally selective nonequilibrium phonon population will enhance or suppress thermal transport. A Knudsen-controlled competition between the increased contribution of long-mean-free-path phonons and excitation-enhanced intrinsic scattering governs the sign of the thermal-conductivity response. First-principles three-phonon scattering rates combined with phonon-tracking Monte Carlo simulations are used to examine Ge, Si, and 3C--SiC from bulk crystals to confined nanofilms. In bulk systems, excitation-enhanced scattering dominates and thermal conductivity is predominantly suppressed. In nanofilms, by contrast, low-frequency excitation can increase the contribution of quasi-ballistic heat-carrying channels and enhance thermal conductivity, whereas higher-frequency excitation is predominantly suppressive. At fixed background temperature and excitation strength, these opposite responses are organized in a frequency--Knudsen map based on the normalized target frequency, $ω_{\mathrm t}/ω_{\mathrm D}$, and the Knudsen number, $\mathrm{Kn}$. The resulting framework provides a general physical basis for controlling nonequilibrium heat transport beyond static phonon engineering.
Comments11 pages, 4 figures
