Supplementary information files for: Anomalous thermal conductivity enhancement in low dimensional resonant nanostructures due to imperfections

Supplementary files for article: Anomalous thermal conductivity enhancement in low dimensional resonant nanostructures due to imperfections.Nanophononic metamaterials have broad applications in fields such as heat management, thermoelectric energy conversion, and nanoelectronics. Phonon resonance in pillared low-dimensional structures has been suggested to be a feasible approach to reduce thermal conductivity (TC). In this work, we study the effects of imperfections in pillared nanostructures based on graphene nanoribbons (GNR), using classical molecular dynamics simulations and harmonic lattice dynamics. The TC of perfect pillared GNR is only about 13% of that of pristine GNR due to the strong phonon resonant hybridization in pillared GNR. However, introducing imperfections such as vacancy defects and mass mismatch between the pillars and the base material, and alloy disorder in the pillars, can weaken the resonant hybridization and abnormally increase the TC. We show that both vacancy defects and mass mismatch can reduce the penetration of the resonant modes from the pillars into the base material, while the alloy disorder in the pillars can scatter the phonons inside them, which turns regular resonance into a random one with weaker hybridization. Our work provides useful insight into the phonon resonance mechanisms in experimentally relevant low dimensional nanostructures containing various imperfections.

论文补充材料：低维共振纳米结构因缺陷引发的异常热导率增强效应。纳米声子超材料在热管理、热电能量转换与纳米电子学等领域拥有广泛应用前景。柱形低维结构中的声子共振被认为是降低热导率（Thermal Conductivity, TC）的可行方案。本研究以石墨烯纳米带（Graphene Nanoribbons, GNR）为基底构建柱形纳米结构，结合经典分子动力学模拟与简谐晶格动力学方法，探究各类缺陷对该结构的影响。由于柱形石墨烯纳米带内部存在强烈的声子共振杂化效应，完美柱形石墨烯纳米带的热导率仅约为原始石墨烯纳米带的13%。然而，引入空位缺陷、柱体与基底材料间的质量失配以及柱体内合金无序等缺陷，会削弱共振杂化效应，进而异常提升热导率。研究表明，空位缺陷与质量失配均可抑制共振模式从柱体向基底的渗透，而柱体内的合金无序则会散射柱内声子，将规则共振转化为杂化效应更弱的随机共振。本研究为实验相关的含各类缺陷的低维纳米结构的声子共振机制提供了极具价值的理论参考。