论文标题
金属弦单分子设备中的可控非弹性电荷传输和射击噪声行为
Conformation Controllable Inelastic Charge Transport and Shot Noise Behavior in Metal-String Single Molecular Devices
论文作者
论文摘要
在实验上，通常会很有趣，以弥补设备构型的构象变化如何影响单分子连接的整体电荷运输行为。基于密度功能理论和非平衡绿色功能形式主义的盟军方法，我们在这里探索了连接异质性对各种基于金属弦的单分子设备中非弹性电荷传输的影响。构成活性元素对谐振水平敏感，过渡金属中心会影响拉伸，弯曲和扭转激发模式，而摇摆和剪裁模式在很大程度上受轴向配体控制。对于某些分子构象和电极取向，可能会出现声子辅助量子干扰效果，从而导致较高的波数振动模式抑制。所得的非弹性光谱可能取决于声子是发射还是吸收的，因此具有主要的FANO共振或抗共振形状。这种纳米级量子干扰效果特别表现在那些金属弦的分子连接处，在那些金属弦线连接处（局部和离域虚拟态之间）在光学声子能量（$δ{e} _ {| homo-lumo | | |} <$ 40 MEV）中很好地存在于此。事实证明，如果通过边界轨道横断道伴随着缓慢的松弛过程后，单分子射击噪声几乎可以表现出几乎泊松的行为。因此，我们的结果表明，可以通过金属中心的选择性结构来调整跨金属弦复合物的电荷传输性能，还可以通过优选的纳米级电极方向来调整纳米级电极的优先考虑，以构建具有理想的可控性的分子设备。
It is often intriguing experimentally to take stock of how conformational changes in the device configuration may impact the overall charge transport behavior of single-molecule junctions. Based on the allied approach of density functional theory and non-equilibrium Green's function formalism, we explore here the effect of junction heterogeneity on inelastic charge transport in various metal-string based single-molecule devices. The constituent active elements being sensitive to the resonant levels, transition metal centers are found to influence stretching, bending, and torsional excitation modes, while rocking and scissoring modes are controlled largely by the axial ligands. For certain molecular conformations and electrode orientations, phonon-assisted quantum interference effect may crop up, leading to the suppression of higher wavenumber vibrational modes. The resulting inelastic spectra are likely to take the shape of dominant Fano resonance or anti-resonance, depending on whether phonons are emitted or absorbed. Such nanoscale quantum interference effect is manifested especially in those metal-string molecular junctions for which the energy gap (between localized and delocalized virtual states) lies well within the optical phonon energies ($Δ{E}_{|HOMO-LUMO|} <$ 40 meV). It also turns out that single molecular shot noise can exhibit nearly Poissonian behavior if the inter-channel tunneling through frontier orbitals is accompanied by phonon absorption or emission following a slow relaxation process. Our results thus suggest that charge transport properties across metal-string complexes can be potentially tuned by selective architecture of the metal centers and also, by preferred orientation of nanoscale electrodes in a bid to build up molecular devices with desirable controllability.
