Thermally driven polaron transport in conjugated polymers
Thermally driven polaron transport in conjugated polymers
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DOI：
10.1103/physrevb.105.014303
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发表时间：
2022-01-07
影响因子：
3.7
通讯作者：
Clark, Stephen R.
中科院分区：
文献类型：
--
作者：
Berencei, Laszlo;Barford, William;Clark, Stephen R.
本文用量子-经典混合方法模拟了共轭聚合物中的电荷-极化子输运。电荷，它耦合到单体的角旋转，通过随时间变化的薛定谔方程建模，而单体通过经典的运动方程处理。此外，该系统是热化的假设单体受到布朗波动的朗之万方程建模。电荷耦合到单体的旋转定位成一个朗道极化子的粒子，而单体的热波动导致极化子动力学。该模型的新兴低能尺度是极化子重组能Er，因此Tr = Er/kB是低温动力学的方便尺度。我们研究两种类型的动力学;都与温度T < Tr有关。在较低的温度制度的系统保持在相同的准绝热状态，对应于无激活极化子扩散的极化子随机沿着链爬行。然而，随着温度的升高，有一个交叉到一个额外的激活转移过程，对应于非绝热状态之间的跳跃。我们表明，这些过程表现出Landau-Zener型动力学。我们注意到，由于我们的模型是通用的，它同样适用于激子-极化子（即，能量）传输，以及准一维分子堆中的电荷和激子极化子传输。
We present a hybrid quantum-classical simulation of charge-polaron transport in conjugated polymers. The charge, which couples to the angular rotations of the monomers, is modeled via the time-dependent Schrodinger equation, while the monomers are treated classically via the Ehrenfest equations of motion. In addition, the system is thermalized by assuming that the monomers are subject to Brownian fluctuations modeled by the Langevin equation. Charge coupling to the monomer rotations localizes the particle into a Landau polaron, while the thermal fluctuations of the monomers causes polaron dynamics. The emergent low-energy scale of the model is the polaron reorganization energy, Er, and thus Tr = Er/kB is a convenient scale for the low-temperature dynamics. We investigate two types of dynamics; both relevant for temperatures T < Tr. In the lower temperature regime the system remains in the same quasidiabatic state, corresponding to activationless polaron diffusion as the polaron crawls stochastically along the chain. As the temperature is raised, however, there is a cross-over to an additional activated transfer process which corresponds to hopping between diabatic states. We show that these processes exhibit Landau-Zener type dynamics. We note that as our model is general, it equally applies to exciton-polaron (i.e., energy) transport in conjugated polymers, and to charge and exciton polaron transport in quasi one-dimensional molecular stacks.