Investigation of electronic properties of novel two-dimensional materials

我们主要研究了三种不同的材料：单层蓝色荧光粉、单层GdAg2和单晶LaBi.单层蓝色荧光粉是通过蒸发黑色荧光粉在干净的Au(111)衬底上生长的。从LEED模式中，我们发现了一个完美的5x5超结构，这与以前的报道很好地一致。ARPES测量证实了在费米能级附近存在带隙。因此，蓝色荧光体是未来纳米器件的一个很好的候选者。单层GdAg2是通过将纯Gd从电子束蒸发器蒸发到干净的Ag(111)衬底上而生长的。以前的MOKE和XMCD测量证实了这种材料的铁磁性。在这里，使用ARPES，我们发现在这个材料中存在一条Weyl节线。我们的理论合作者证实了我们的发现。目前，稿件已经提交，正在进行评审。LaBi是拓扑绝缘体的候选对象。以前的实验已经报道了一些关于能带结构的ARPES结果，并得出了Labi具有拓扑Dirac锥的结论。然而，在这里，我们用高分辨率的ARPES和第一性原理计算研究了Labi的表面态。我们发现，通过能带杂化，其他拓扑的非平凡表面态被隔开，表面态看起来像狄拉克节线。这项研究已经发表在《物理评论B》上。[物理。版本B 97,155153(2018年)]

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)]