低维微纳尺度体系声子热传导和热调控:来自芯片散热的非平衡统计物理问题

半导体芯片发展路线图上的一个障碍是“热死(heat death)”,也就是大量热量的产生而导致芯片被烧毁.所以散热问题成为进一步发展半导体工业亟待解决的关键问题.芯片里的热传导包含一维和二维材料中声子热传导以及声子通过不同材料间的界面热传导.本文总结了过去30年来一维、二维和界面声子热传导的主要理论和实验进展,重点介绍了一维体系声子热传导发散的物理机制以及反常热传导和反常扩散之间的关系.本文还简要讨论了与此相关的非平衡态统计物理的基本问题:从给定的哈密顿量出发是否能够推导出宏观输运行为.本文从微观图像的角度讨论了调控声子热传导的几种方法:纳米声子晶体,纳米热超材料,界面和声子凝聚等.为了让读者全面了解声子热传导,还简要地介绍了其他声子热输运现象,包括热导量子化、声子热霍尔效应、手性声子,以及声子与其他载流子之间的相互作用.最后,本文讨论了声子热传导研究面临的挑战和机遇,包括声子在量子信息和技术中的潜在应用.     

Perturbative Treatment for Stationary State of Local Master Equation

The local approach to construct master equation for a composite open system with a weak internal coupling is simple and seems reasonable. However, it is thermodynamic consistent only when the subsystems are resonantly coupled. Efforts are being made to understand the inconsistency and test the validity of the local master equation. We present a perturbative method to solve the steady-state solutions of linear local master equations, which are demonstrated by two simple models. The solving process shows the stationary state as the result of competition between incoherent operations and the unitary creating quantum coherence, and consequently relate quantum coherence with thermodynamic consistency.