电子关联在手性诱导分子结自旋选择性中的作用

中文摘要 AI 辅助

非平衡格林函数（NEGF）方法被应用于一个螺旋几何结构中的Hubbard原子链，该链夹在两个电极之间，其中一个电极是磁性的，以评估分子内电子关联效应在解释手性诱导自旋选择性（CISS）效应中可能扮演的角色。关联效应在自洽二阶Born近似的水平上处理。讨论了螺旋的两种手性：左旋（L）和右旋（D）。此外，我们使用Kane和Mele的简化模型考虑了链内的自旋轨道耦合（SOC），该模型利用了弯曲几何固有的次近邻相互作用。与电极的相互作用在宽频带近似下考虑。我们考虑了Hubbard常数U与沿链原子位点间跳跃t之比U/t，该比值最高取到2，但在我们的计算中发现了非常小的自旋极化。尽管定义为最大和最小总电流之间相对差的自旋极化因子对两种对映体而言几乎相同，但达到最大和最小电流所需的尖端极化方向对两种对映体是不同的。还发现，只有自洽地考虑二阶微扰理论，才能与观测结果定性一致。还讨论了不同U/t比值下链原子上自旋布居的分布。本研究得出结论，尽管考虑电子-电子相互作用对于理解分子结内的自旋选择性很重要，但它们不能单独解释实验中观察到的高自旋极化因子。

英文摘要

The Non-Equilibrium Green's Function (NEGF) approach is applied to a chain of Hubbard atoms in a helical geometry sandwiched between two leads, one of which is magnetic, to assess what role the electronic correlation effects within the molecule may play in explaining the Chirality Induced Spin Selectivity (CISS) effect. The correlation effects are treated at the level of the self-consistent second Born approximation. Two chiralities, Laevorotatory (L) and Dextrorotatory (D), of the helix, are discussed. Further, we account for spin-orbit coupling (SOC) within the chains using a simplified model of Kane and Mele that exploits next-nearest neighbour interactions intrinsic to a curved geometry. The interaction with the leads is considered within the Wide Band Approximation. We consider the ratio, U/t, of the Hubbard constant U to the hopping t between atomic sites along the chain of up to two, but found very little spin polarisation in our calculations. Even though the spin polarisation factor defined as a relative difference between the largest and smallest total current is found for both enantiomers practically the same, the orientation of the tip's polarisation required to reach the largest and smallest currents for the two enantiomers differed. It is also found that the qualitative agreement with observations can only be achieved if we account, self-consistently, for the second order of the perturbation theory. The distribution of the spin populations on the chain atoms for different U/t ratios is also discussed. This study concludes that even though accounting for electron-electron interactions are important in understanding spin selectivity within molecular junctions, they cannot be made solely responsible for the high spin polarisation factors observed in experiments.

发表机构

• King’s College London（伦敦国王学院）
• Uppsala University（乌普萨拉大学）

机构由 AI 辅助整理，请以论文原文为准。