Experimental Observations Indicating the Topological Nature of the Edge States on HfTe_5

The topological edge states of two-dimensional topological insulators with large energy gaps furnish ideal conduction channels for dissipationless current transport. Transition metal tellurides X_(Te5)X=Zr, Hf) are theoretically predicted to be large-gap two-dimensional topological insulators, and the experimental observations of their bulk insulating gap and in-gap edge states have been reported, but the topological nature of these edge states still remains to be further elucidated. Here, we report our low-temperature scanning tunneling microscopy/spectroscopy study on single crystals of HfTe5. We demonstrate a full energy gap of ～80 meV near the Fermi level on the surface monolayer of HfTe5 and that such an insulating energy gap gets filled with finite energy states when measured at the monolayer step edges. Remarkably, such states are absent at the edges of a narrow monolayer strip of one-unit-cell in width but persist at both step edges of a unit-cell wide monolayer groove. These experimental observations strongly indicate that the edge states of HfTe5 monolayers are not trivially caused by translational symmetry breaking, instead they are topological in nature protected by the 2 D nontrivial bulk properties.     

GC4001A气相色谱仪使用时常见问题及注意事项

在使用气相色谱仪时,了解仪器的工作原理,电、气路的流程对于仪器的正确使用非常重要,如样品出峰迟缓,可以提高载气流速;杂峰多,可以加大阻值等减小干扰;氢焰检测器点不着火,可以调节氧、氢气比例等。以下笔者结合实际经验,介绍了使用GC4001A气相色谱仪(北京东西电子分析仪器公