Decorating two-dimensional (2D) materials with transition-metal adatoms is an effective way to bring about new physical properties that are intriguing for applications in electronics and spintronics devices. Here, we systematically studied the coverage-dependent magnetic and electronic properties of graphene decorated by Co adatoms, based on first-principles calculations. We found that if the Co coverage is larger than 1/3ML, the Co atoms will aggregate to form a Co monolayer and then a van der Waals bilayer system between the Co monolayer and graphene forms. When the Co coverage is ≤1∕3ML, the Co adatom is spin-polarized with spin moment varying from 1.1 to 1.4μB. The dxz∕yz and dxy∕x2−y2 orbitals of Co hybridize significantly with the π bands of graphene, which generates a series of new bands in the energy range from −2eV to 1eV with respect to the Dirac point of graphene. In most cases, the new bands near the Fermi level lead to topological states characterized by the quantum anomalous Hall effect.

中文翻译：

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具有Co吸附原子的石墨烯的覆盖率依赖性磁性和电子特性

用过渡金属吸附原子装饰二维 (2D) 材料是一种有效的方法，可以带来新的物理特性，这些特性对于电子和自旋电子器件的应用很有吸引力。在这里，我们基于第一性原理计算系统地研究了由 Co 吸附原子修饰的石墨烯的覆盖范围相关的磁性和电子特性。我们发现如果 Co 覆盖率大于 1/3ML，Co原子将聚集形成Co单层，然后在Co单层和石墨烯形式之间形成范德华双层系统。当 Co 覆盖范围为≤1∕3ML，Co 吸附原子是自旋极化的，自旋矩从 1.1 变化到 1.4μ乙. 这dXz∕是的z和dX是的∕X2-是的2Co 的轨道与π石墨烯带，它在能量范围内产生一系列新带-2eV 为 1eV相对于石墨烯的狄拉克点。在大多数情况下，费米能级附近的新能带会导致以量子反常霍尔效应为特征的拓扑状态。