题目：From Weyl semimetal to Dirac semimetal in HgCr₂Se_3.5Te_0.5

报告人：虞祥龙 (南方科技大学）

时间：2017年1月20日上午10:00

地点：固体所新楼520会议室

 Abstract:
Weyl semimetal has recently attracted enormous attention due to their unusual features. So far, this novel state has been predicted theoretically and confirmed experimentally in several materials, such as HgTe, LaPtBi, Y₂Ir₂O₇, TaAs, TaP, NbAs, NbP and HgCr₂Se₄. Doping plays an important role in the research of condensedmatter materials. However, its influence on the Weyl semimetal has been little investigated. Here, we present detailed first-principles and theoretical studies on HgCr₂Se₄  with doping of Te atoms at the Se sites. A special case where only one pair of crossing points locates at the Fermi level is realized in HgCr₂Se_3.5Te_0.5 where one of the Se atoms in the primitive unit cell is replaced by a Te atom. A further study of k·p theory shows that the two points constitute a pair of Weyl nodes with opposite chiralities in the momentum space, and only one edge state and one single Fermi arc are obtained at each boundary of a film. Moreover, through investigations and analyses of different doping cases of HgCr₂Se_3.5Te_0.5 , we find that when the type of doping induces inversion symmetry or positional disorder, the Weyl nodes transform into Dirac points resulting in a change from a Weyl semimetal to a Dirac semimetal.

Reference：

X. L. Yu(虞祥龙), Y. J. Jin, J. Wu*; Theoretical study of HgCr₂Se_3.5Te_0.5: a doping-site-dependent semimetal; Sci. Rep. 6, 30866 (2016). [link]