半Heusler型Na_(1-x)Cs_xAlGe(0≤x≤1)合金能带反转结构的研究

Band inversion in half Heusler-type Na_(1-x)Cs_x AlGe(0≤x≤1)

采用第一性原理的计算方法,研究了全部由轻元素构成的半Heusler型NaAlGe合金中,掺杂元素对合金拓扑能带结构的影响.发现利用同族的Cs元素掺杂替换Na元素,能够诱导Na1-x Csx AlGe合金的能带结构由原本正常带序(0 x<0.125)转换为反转带序(0.125 x 1).基于对这一现象的深入讨论,我们提出在几乎没有自旋-轨道耦合作用的材料中,掺杂元素(Cs)是通过其离子半径的不同,进而影响晶格参数变化导致另外两种近邻原子间杂化作用发生变化,来诱导拓扑反带结构形成的.

The infiuences of doping whit congeners on the band topology in half Heusler-type of NaAlGe alloys are investigated using the first-principles calculations. It is found that the Na1-xCsx AlGe alloys with a normal band order are converted into topological nontrivial phases when x is up to 0.125. We argue that it is the degree of hybridization between Al and Ge determine the band order at the Fermi level. The Na or Cs only plays a role of the valence electron contributor and infiuences the lattice parameter.