Subnanoscale Engineering of 2D Magnetism in van der Waals Heterostructures

范德华(VDW)异质结构是一种人工构建的结构，它将原子薄层与独特的本征性质结合在一起，如自旋轨道分裂电子能带或超导。这些堆栈由原子锐利的接口组成，可以承载从组成层的非平凡组合中出现的支持邻近的物理现象。2017年，本征铁磁性2D层的发现提供了一个重要的基础，它开辟了一类全新的利用自旋自由度的可设计VDW异质结构。在这个项目中，我们提出了一个由2D磁层与具有大的自旋-轨道相互作用的层接触组成的VDW双层膜的联合理论和实验表征，我们的目标是首先研究具有大的自旋-轨道相互作用的VDW层的邻近效应是否可以增强2D磁体的磁各向异性能量或磁交换相互作用，以提高其铁磁居里温度或稳定非铁磁状态。其次，我们计划逆转这种相互作用，并利用从2D磁体到第二层的拓扑属性的邻近感应磁性。为了达到我们的目标，我们计划使用基于含时密度泛函理论和多体微扰理论的第一性原理方法来计算和探索候选双层的电子、磁和输运性质，重点是磁性层间和层内相互作用。在这些计算中，我们计划超越基态模拟，获得像局部自旋翻转过程这样的动力学性质，以及像磁子这样的集体激发以及它们与电子的相互作用。展望未来，我们还将解决由多层组成的更复杂的异质结构。作为补充，我们计划组装包含2D磁体和由具有较强自旋-轨道相互作用的相对较重的元素组成的双层。随后，我们将使用低温组合扫描隧道(STM)和原子力显微镜(AFM)对其结构、电子和磁性进行详细表征。这里最重要的是STM/AFM获得纳米级信息的独特能力，这使我们能够深入研究邻近效应和边缘效应，以及检测复杂的有序磁结构。我们期望我们提出的理论和实验之间的共生将为包含2D磁体的VDW异质结构的新领域奠定基础。

Van der Waals (vdW) heterostructures are artificially built structures which combine atomically thin layers with distinct intrinsic properties such as spin-orbit-split electronic bands or superconductivity. These stacks consist of atomically sharp interfaces and can host proximity-enabled physical phenomena that emerge from the non-trivial combination of the constituent layers. The discovery of intrinsically ferromagnetic 2D layers in 2017 supplied one important building block which opened a whole new class of designable vdW heterostructures utilising the spin degree of freedom. In this project, we propose a joint theoretical and experimental characterization of vdW bilayers consisting of a 2D magnetic layer in contact to a layer which possesses large spin-orbit interactions.Our goals for this proposal is to study firstly whether proximity effects from a vdW layer with large spin-orbit interaction can enhance the magnetic anisotropy energy or the magnetic exchange interactions of an 2D magnet, with the goal of raising its ferromagnetic Curie temperature or stabilizing non-ferromagnetic states. Secondly, we plan to reverse the interaction and exploit proximity-induced magnetism from a 2D magnet onto the topological properties of a second layer. To reach our goals we plan to use first-principle methods based on time-dependent density functional theory combined with many-body perturbation theory to compute and explore the electronic, magnetic and transport properties of candidate bilayers with the focus on the magnetic inter- and intralayer interactions. In these calculations we plan to go beyond ground state simulations to access dynamical properties like local spin flip processes as well as collective excitations like magnons and their interactions with electrons. Looking ahead, more complex heterostructures consisting of several layers will also be addressed.Complementary, we plan to assemble bilayers containing a 2D magnet and a layer consisting of relatively heavy elements with strong spin-orbit interaction. Subsequently, we will use low-temperature combined scanning tunneling (STM) and atomic force microscopy (AFM) for a detailed characterization of the structural, electronic, and magnetic properties. Essential here is the unique capabilities of the STM/AFM to obtain information at thenanometer scale which enables us to dive in detail into proximity and edge-effects as well as to detect complexly ordered magnetic structure. We expect that our proposedsymbiosis between theory and experiment will establish the foundation of a new field of vdW heterostructures incorporating 2D magnets.