自旋极化STM调控单分子尺度局域量子态的理论研究

利用自旋极化扫描隧道显微镜（SP-STM）实现单分子尺度局域自旋态的精确调控，是量子调控领域的前沿和热点。铁磁性探针与局域量子掺杂之间的磁性交换耦合会诱发很多新奇的物理现象。然而，能解释实验现象潜在机制的物理细节很难从实验中获取，且目前的理论工作多集中于模型计算。本项目拟设计方案嵌套使用密度泛函理论，级联运动方程方法和完全活化空间自洽场方法，精准模拟SP-STM对“分子/表面”复合体系的量子态调控过程。在原子水平上提供调控过程中体系几何与电子结构变化的细节，研究探针顶端形貌和顶端电子结构对调控结果的影响；探索自旋极化条件下Kondo效应和非弹性自旋激发过程，并深度解析实验现象；总结计算方法和调控技巧，形成一套应用于“分子-表面”复合体系量子态调控的比较成熟的理论手段。本项目的完成将为SP-STM调控实验提供独到的见解，并且有助于在一些新型的量子功能材料或器件中实现更为复杂的量子态调控设计。

Applying spin-polarized scanning tunneling microscopy (SP-STM) to characterize and control the local spin states in complex systems, has become one of the research focuses in the field of quantum manipulation. The magnetic exchange coupling between spin-polarized tip and the local spin impurity induces novel physical phenomena, such as the asymmetric Kondo splitting. However, because the physical details (geometric and electronic structures) are difficult to obtain from experiments, and the theoretical works generally focus on model Hamiltonian calculations，the underlying mechanisms of physical phenomena remain somewhat unclear. In this project, based on density functional theory (DFT), supplemented by hierarchical equations of motion (HEOM) approach and complete active space self-consistent field (CASSCF) method , we will investigate theoretically the SP-STM control of quantum states in “molecule/surface ”composite system. We will elucidate the evolution of geometric and electronic structures of the composite junction in the process of tip displacement, explore the influence of tip geommetry and tip material on the quantum behavior of complex system, reveal the underlying mechanisms of the asymmetric Kondo splitting and inelastic spin excitation, and finally form a set of mature theoretical means for the simulation of "molecule / surface" composite systems. The understanding and insight provided by the first-principles-based simulation may help to realize more fascinating quantum state manipulations in advanced functional materials and devices.