通过分子导线的相干电荷输运：导线中电子激发的“激子阻断”和电流
Coherent charge transport through molecular wires: "Exciton blocking" and current from electronic excitations in the wire
摘要：
我们考虑激子对分子纳米结中电流的影响，使用一个模型，包括两个两级网站桥连接自由电子水库。将密度算符展开到非耦合点的多电子本征态中，得到桥子空间中的16 × 16密度矩阵，其动力学由Liuoville方程控制，该方程考虑了桥上的相互作用以及电子注入和阻尼。利用李群SU（2）的对称性，我们的研究可以大大简化。我们研究了偏置电压，库仑排斥和能量转移相互作用对稳态电流的影响，特别是专注于桥位之间的激子相互作用的效果。我们的计算表明，在非相互作用的电子的情况下，这种相互作用导致在高电压下的电流减少的同二聚体桥。换句话说，我们预测了\textquotedblleft激子\textquotedblright阻断的效果。\textquotedblleft激子\textquotedblright阻断的效果被修改为异二聚体桥，并消失为强库仑排斥的网站。在后一种情况下，激子型相互作用可以为电子传导打开新的通道。特别是，在强库仑排斥的情况下，即使当电子连接性不存在时，也存在传导。
英文摘要：
We consider exciton effects on current in molecular nanojunctions, using a model comprising a two two-level sites bridge connecting free electron reservoirs. Expanding the density operator in the many-electron eigenstates of the uncoupled sites, we obtain a 16X16 density matrix in the bridge subspace whose dynamics is governed by Liuoville equation that takes into account interactions on the bridge as well as electron injection and damping to and from the leads. Our consideration can be considerably simplified by using the pseudospin description based on the symmetry properties of Lie group SU(2). We study the influence of the bias voltage, the Coulomb repulsion and the energy-transfer interactions on the steady-state current and in particular focus on the effect of the excitonic interaction between bridge sites. Our calculations show that in case of non-interacting electrons this interaction leads to reduction in the current at high voltage for a homodimer bridge. In other words, we predict the effect of \textquotedblleft exciton\textquotedblright blocking. The effect of \textquotedblleft exciton\textquotedblright blocking is modified for a heterodimer bridge, and disappears for strong Coulomb repulsion at sites. In the latter case the exciton type interactions can open new channels for electronic conduction. In particular, in the case of strong Coulomb repulsion, conduction exists even when the electronic connectivity does not exist.
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