Prediction of Topological Dirac Semimetal in Ca-based Zintl Layered Compounds CaM₂X₂ (M = Zn or Cd; X = N, P, As, Sb, or Bi)

Liang-Ying Feng^1*, Rovi Angelo B. Villaos¹, Aniceto B. Maghirang III¹, Zhi-Quan Huang¹, Chia- Hsiu Hsu^1,2, Hsin Lin³, Feng-Chuan Chuang^1,2,4

¹Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan
²Physics Division, National Center for Theoretical Sciences, Taipei, Taiwan
³Institute of Physics, Academia Sinica, Taipei, Taiwan
⁴Department of Physics, National Tsing Hua University, Hsinchu, Taiwan

* Presenter:Liang-Ying Feng, email:zxc6981189@g-mail.nsysu.edu.tw

Topological Dirac materials are attracting a lot of attention because they offer exotic physical phenomena. An exhaustive search coupled with first-principles calculations was implemented to investigate 10 Zintl compounds with a chemical formula of CaM2X2 (M = Zn or Cd, X = N, P, As, Sb, or Bi) under three crystal structures: CaAl₂Si₂-, ThCr₂Si₂-, and BaCu₂S₂-type crystal phases. All of the materials were found to exhibit CaAl₂Si₂-type structure based on total ground state energy calculations. Symmetry-based indicators are used to evaluate their topological properties. Interestingly, we found that CaM₂Bi₂ (M = Zn or Cd) are topological crystalline insulators. Calculations under the hybrid functional approach show that they are topological Dirac semimetals, where four-fold degenerate Dirac points are located along the symmetry line between Г to A points. Finally, phonon spectra calculations revealed that CaCd₂Bi₂ is thermodynamically stable. The Zintl phase of AM₂X₂ compounds have not been identified in any topological material databases, thus can be a new playground in the search for new topological materials.

Keywords: Topological Dirac Semimetal, Zintl Materials, AM₂X₂, Surface States, Density Functional Theory