Investigation of electronic properties of novel two-dimensional materials

我们主要研究了三种不同的材料：单层蓝色磷光烯、单层GdAg2和单晶LaBi。单层蓝色磷光烯是通过将黑色磷光烯片蒸发到干净的Au（111）衬底上来生长的。从LEED模式中，我们发现了一个完美的5x5上层建筑，这与之前的报告非常吻合。ARPES的测量证实了费米能级附近存在带隙。因此，蓝色磷光烯是未来纳米器件的良好候选材料。手稿仍在准备中。通过将纯Gd从电子束蒸发器蒸发到清洁的Ag（111）衬底上来生长单层GdAg2。先前的MOKE和XMCD测量已经证实了这种材料的铁磁顺序。在这里，使用ARPES，我们发现该材料中存在Weyl节点线。我们的理论合作者证实了我们的发现。现在，手稿已经提交，正在审核中。LaBi是一种拓扑绝缘体候选者。前人的实验报道了一些关于带结构的ARPES结果，并得出LaBi具有拓扑狄拉克锥的结论。然而，在这里，我们通过高分辨率ARPES和第一性原理计算研究了LaBi的表面态。我们发现，原本拓扑的非平凡表面态通过带杂化而被间隙化，表面态看起来像狄拉克节点线。这项研究已经发表在《物理评论b》上。rev B 97, 155153 (2018)]

We mainly investigated three different materials: monolayer blue phosphene, monolayer GdAg2 and single crystal LaBi.Monolayer blue phosphene is grown by evaporating pieces of black phosphene onto a clean Au(111) substrate. From the LEED pattern, we find a perfect 5x5 superstructure, which is in good agreement with previous reports. The ARPES measurements have confirmed the existence of a band gap near the Fermi level. So blue phosphene is a good candidate for future nanodevices. The manuscript is still under preparation.Monolayer GdAg2 is grown by evaporating pure Gd from a e-beam evaporator onto a clean Ag(111) substrate. Previous MOKE and XMCD measurements have confirmed the ferromagnetic order in this material. Here, using ARPES, we found the existence of a Weyl nodal line in this material. Our theoretical collaborator confirmed our findings. Now, the manuscript has been submitted and is under review.LaBi is a topological insulator candidate. Previous experiments have reported some ARPES results on the band structures and concluded that LaBi have topological Dirac cones. However, here we studied the surface states of LaBi by high-resolution ARPES and first-principles calculations. We found that the otherwise topological nontrivial surface states are gapped out by band hybridization and the surface states looks like a Dirac nodal line. This work has already been published in Physical Review B. [Phys. Rev. B 97, 155153 (2018)]