Lee Chee Kong, Moix Jeremy, Cao Jianshu
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
J Chem Phys. 2015 Apr 28;142(16):164103. doi: 10.1063/1.4918736.
Quantum transport in disordered systems is studied using a polaron-based master equation. The polaron approach is capable of bridging the results from the coherent band-like transport regime governed by the Redfield equation to incoherent hopping transport in the classical regime. A non-monotonic dependence of the diffusion coefficient is observed both as a function of temperature and system-phonon coupling strength. In the band-like transport regime, the diffusion coefficient is shown to be linearly proportional to the system-phonon coupling strength and vanishes at zero coupling due to Anderson localization. In the opposite classical hopping regime, we correctly recover the dynamics described by the Fermi's Golden Rule and establish that the scaling of the diffusion coefficient depends on the phonon bath relaxation time. In both the hopping and band-like transport regimes, it is demonstrated that at low temperature, the zero-point fluctuations of the bath lead to non-zero transport rates and hence a finite diffusion constant. Application to rubrene and other organic semiconductor materials shows a good agreement with experimental mobility data.
利用基于极化子的主方程研究了无序系统中的量子输运。极化子方法能够将由雷德菲尔德方程支配的相干带状输运 regime 的结果与经典 regime 中的非相干跳跃输运联系起来。观察到扩散系数作为温度和系统 - 声子耦合强度的函数呈现非单调依赖性。在带状输运 regime 中，扩散系数与系统 - 声子耦合强度呈线性比例关系，并且由于安德森局域化在零耦合时消失。在相反的经典跳跃 regime 中，我们正确地恢复了由费米黄金定则描述的动力学，并确定扩散系数的标度取决于声子浴弛豫时间。在跳跃和带状输运 regime 中均表明，在低温下，浴的零点涨落导致非零的输运速率，从而产生有限的扩散常数。应用于红荧烯和其他有机半导体材料时，与实验迁移率数据显示出良好的一致性。
