基于单分子磁体和石墨烯纳米带构建超分子自旋阀的理论设计与性能调控

Recently，the research focus and cutting-edge field of spintronics is to design spin valves by molecular materials and make them implement a specific function. However, for molecular spin valves, experimental and theoretical studies mainly focus on a ferromagnetic metal/molecule/ferromagnetic metal sandwich structure model which has many disadvantages. Therefore, in this project, we construct supramolecular spin valves based on single-molecule magnets and graphene nanoribbons, which acts as an improvement program for the limitations of the ferromagnetic metal/molecule/ferromagnetic metal sandwich structure model. By applying density-function theory, nonequilibrium Green's functions, and molecular dynamics method, we will firstly investigate the most probable adsorption configuration of single-molecule magnets and graphene nanoribbons. Then, we will explore the internal physical mechanisms of supramolecular spin valve and get some systematic knowledge about their microscopic mechanisms. At last, in order to tune the performance of supramolecular spin valves, we will change the matching relations of energy levels between graphene nanoribbons and single-molecule magnets by doping heterogeneous atoms or edge modification in graphene nanoribbons. Our research may provide physical models and theoretical basis for the actual preparation of supramolecular spin valves based on single-molecule magnets and graphene nanoribbons.

近些年来，通过分子材料设计自旋阀并实现特定功能已经成为自旋电子学领域的研究热点和前沿。然而，目前实验和理论上研究的分子自旋阀主要是基于铁磁金属/分子/铁磁金属的三明治结构模型，这种构型的自旋阀存在着诸多缺陷。因此，本项目提出将单分子磁体和石墨烯纳米带相结合构建超分子自旋阀，以此作为对铁磁金属/分子/铁磁金属三明治结构模型局限性的改进方案。我们将以密度泛函理论和非平衡格林函数为基础，结合分子动力学方法，先研究单分子磁体在石墨烯纳米带上的最概然吸附构型；然后对超分子自旋阀的内部物理机理进行深层次的理论研究，使其微观机理得到一个系统的认识；最后通过异质原子取代掺杂或者边缘修饰方法使石墨烯纳米带与单分子磁体间能级匹配关系发生改变，实现对超分子自旋阀电学性能的调控。本研究将为实际制备基于单分子磁体和石墨烯纳米带的超分子自旋阀提供物理模型和理论基础。

开发高性能自旋电子器件是目前分子电子学领域的最前沿。本项目着眼于这一前沿研究，提出了分子自旋阀器件的理论设计方案，并对相应的自旋输运机理做了深入的探索。主要研究内容包括：（1）基于二茂铁单分子磁体和石墨烯纳米带构建超分子自旋阀的理论设计、性能调控与自旋输运机理研究；（2）探索碳原子链的奇偶效应对基于石墨烯纳米带或单分子磁体的分子自旋阀的电学性能影响；（3）研究电场、光照、磁场、氢化等外部调控方式对分子自旋阀电学性能的影响。我们的研究发现：（1）基于二茂铁和石墨烯纳米带能够得到结构稳定、性能优越的超分子自旋阀，而石墨烯纳米带的掺杂类型是实现高性能分子自旋阀的关键因素；（2）碳原子链的奇偶效应能够诱导分子自旋阀中的自旋过滤效率和磁致电阻率出现奇偶振荡特征；（3）电场和光照能够诱导分子空间几何结构的改变，进而实现对分子自旋阀性能的调控；（4）磁场、氢化在保持分子结构的基础上，同样可以有效地调控分子自旋阀的电学性能。这些成果在自旋电子学领域有较重要的应用价值。