Galperin Michael, Nitzan Abraham
P.M. Gross Chemical Laboratory, Duke University, Durham, North Carolina, USA.
Ann N Y Acad Sci. 2003 Dec;1006:48-67. doi: 10.1196/annals.1292.003.
Electron-electron interaction is an essential issue in predicting the properties of a molecular conduction junction. An accurate treatment requires taking proper account of the potential distribution across the junction as well as for the change in electronic structure under the external voltage drop. Another important point is the necessity to treat molecules as open quantum systems. In this paper we address these issues within the framework of the non-equilibrium Green's function formalism at the Hartree-Fock level (NEGF-HF), which permits a self-consistent treatment of the problem. We apply the method to study the experimentally observed asymmetry in the I-V curves with respect to polarity of voltage bias in Hg-Au junctions containing bilayers of alkanethiols of various chain lengths. The origin of the effect is suggested to be the asymmetric behavior of the character of the highest occupied molecular orbital (HOMO) of the junction at opposite biases, which leads to different effective barriers for electron transfer across the junction at opposite signs of the voltage drop. The calculated potential profile shows the capacitor-like nature for the junction with the weak link.
电子-电子相互作用是预测分子传导结性质时的一个关键问题。准确的处理需要适当考虑结两端的电势分布以及外部电压降作用下电子结构的变化。另一个要点是必须将分子视为开放量子系统。在本文中，我们在哈特里-福克水平的非平衡格林函数形式体系（NEGF-HF）框架内探讨这些问题，该形式体系允许对问题进行自洽处理。我们应用此方法研究了含不同链长的烷硫醇双层的汞-金结中，实验观测到的电流-电压（I-V）曲线相对于电压偏置极性的不对称性。该效应的起源被认为是结在相反偏置下最高占据分子轨道（HOMO）特征的不对称行为，这导致在电压降符号相反时电子穿过结的有效势垒不同。计算得到的电势分布表明含弱连接的结具有类似电容器的性质。
