中间相干-非相干电荷输运：DNA的实例研究
Intermediate coherent-incoherent charge transport: DNA as a case study
摘要：
利用Büttiker探针技术研究了金属-分子-金属结中的中间量子相干-非相干电荷输运机制。这个工具使我们能够包括在一个可控的方式不相干的影响，从而研究部分退相干影响电荷转移动力学的情况。受DNA分子中的中间相干-非相干电荷传导实验的启发[L. Xiang {\it et al.}，7，221 - 226（2015）]，我们关注两种代表性结构：交替（GC）$_n$和堆叠的G $_n$ C $_n$序列;后一种结构被认为支持G片段内的电荷离域，从而支持中间相干-非相干传导。我们从一个高度简化的一维紧束缚模型开始分析，同时通过Büttiker的探针引入环境效应。这种极小模型使我们能够获得基本的了解的运输机制，并得出分析结果的分子阻力在不同的限制。然后，我们使用一个更详细的阶梯模型哈密顿来表示双链DNA结构-与环境的影响捕获Büttiker的探针。我们发现，跳跃传导占主导地位的交替序列，而在堆叠序列电荷离域（可视化直接通过电子密度矩阵）支持显着的共振弹道电荷动力学的奇偶效应和电阻的弱距离依赖性反映。我们的分析表明，从极小模型中吸取的经验教训有助于解释DNA中的电荷动力学。
英文摘要：
We study an intermediate quantum coherent-incoherent charge transport mechanism in metal-molecule-metal junctions using Büttiker's probe technique. This tool allows us to include incoherent effects in a controlled manner, and thus to study situations in which partial decoherence affects charge transfer dynamics. Motivated by recent experiments on intermediate coherent-incoherent charge conduction in DNA molecules [L. Xiang {\it et al.}, Nature Chem. 7, 221-226 (2015)], we focus on two representative structures: alternating (GC)$_n$ and stacked G$_n$C$_n$ sequences; the latter structure is argued to support charge delocalization within G segments, and thus an intermediate coherent-incoherent conduction. We begin our analysis with a highly simplified 1-dimensional tight-binding model, while introducing environmental effects through Büttiker's probes. This minimal model allows us to gain fundamental understanding of transport mechanisms and derive analytic results for molecular resistance in different limits. We then use a more detailed ladder-model Hamiltonian to represent double-stranded DNA structures---with environmental effects captured by Büttiker's probes. We find that hopping conduction dominates in alternating sequences, while in stacked sequences charge delocalization (visualized directly through the electronic density matrix) supports significant resonant-ballistic charge dynamics reflected by an even-odd effect and a weak distance dependence for resistance. Our analysis illustrates that lessons learned from minimal models are helpful for interpreting charge dynamics in DNA.
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