Department of Chemical System Engineering, Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan.
J Chem Phys. 2013 Jul 28;139(4):044711. doi: 10.1063/1.4816476.
We study the transport properties of single-walled carbon nanotubes (SWCNTs) using the nonequilibrium Green's function method based on first-principles calculations. We compared three SWCNTs with different chiralities (3, 3), (5, 0), and (4, 2), and found that the thermal conductance varies significantly with the chirality, especially at low temperatures. Such differences are attributed to the dependence on the chirality of the frequency of the lowest optical mode and phonon-phonon interaction with the semi-infinite leads. To obtain accurate low-vibrational frequencies, a force constant correction based on the Lagrange undetermined multiplier method was employed. The phonon-phonon interaction was analyzed in terms of the projection of the phonon coupling with the semi-infinite leads onto the normal modes of the center region. Our result indicates that high optical mode frequency and weak phonon coupling on the armchair (3, 3) SWCNT are the origin of the long quantized plateau found in the experimental thermal conductance.
我们使用基于第一性原理计算的非平衡格林函数方法研究了单壁碳纳米管（SWCNT）的输运性质。我们比较了三种具有不同手性（3,3）、（5,0）和（4,2）的 SWCNT，发现热导随手性有显著变化，特别是在低温下。这种差异归因于最低光学模式频率对手性的依赖性以及与半无限引线的声子-声子相互作用。为了获得准确的低振动频率，采用了基于拉格朗日未定乘数法的力常数修正。通过将声子与半无限引线的耦合投影到中心区域的正则模式上，对声子-声子相互作用进行了分析。我们的结果表明，扶手椅（3,3）SWCNT 中较高的光学模式频率和较弱的声子耦合是实验热导中发现的长量子平台的起源。
