Prediction of topological Dirac semimetal in Ca-based Zintl layered compounds CaM2X2 (M = Zn or Cd; X = N, P, As, Sb, or Bi)

Abstract

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 energetically prefer the 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. Further calculations under the hybrid functional approach and analysis using k · p model reveal that they exhibit topological Dirac semimetal (TDSM) states, where the four-fold degenerate Dirac points are located along the high symmetry line in-between Г to A points. These findings are verified through Green's function surface state calculations under HSE06. 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.

The Zintl phase compounds AEIn2As2 (AE = Ca, Sr, Ba): topological phase transition under pressure

“…24,25 It proposes that the Zintl CaAl 2 Si 2 type material CaM 2 Bi 2 (M = Zn or Cd) is a topological insulator. 26 The AM 2 X 2 (A = Ca, Sr, or Ba; M = Zn or Cd; X = Sb or Bi) series of materials were confirmed as topological insulators with band inversion and the coexistence of insulating topological state and the Rashba effect in the BaCd 2 SbBi film was achieved. 27 Inspired by SrX 2 As 2 (X = Cd, Sn) non-magnetic materials, we propose the new idea that AEIn 2 As 2 (AE = Ca, Sr, Ba) topological insulators may also undergo topological quantum phase transitions or metal–insulator phase transitions.…”

High Thermoelectric Performance in 2D Technetium Dichalcogenides TcX2 (X = S, Se, or Te)

“…In the past decades, with the development of theoretical simulation and synthesis methods, some 2D materials have been successfully studied both theoretically and experimentally . These materials are black phosphorus, transition-metal dichalcogenides (TMDs), − Janus TMDs, − group IVA–VA compounds, MXenes, , and Zintl compounds. − These 2D materials exhibit various outstanding properties. Thus, they have been successfully used in electronic, optoelectronic, and TE applications. , Also, these materials can be experimentally synthesized using various growth methods, such as epitaxial growth, chemical vapor deposition, mechanical exfoliation, and micromechanical cleavage .…”

Large Gap Topological Insulating Phase and Anisotropic Rashba and Chiral Spin Textures in Monolayer Zintl A2MX2

“…Several comprehensive technical reviews on TIs − have been conducted. Moreover, numerous theoretical studies have demonstrated promising results, which include materials exhibiting honeycomb-like phases such as III–V buckled honeycombs, bismuthene, and graphene, , MXenes, − transition metal dichalcogenides (TMDs), organometallic frameworks, Janus materials, , ternary transition metal chalcogenides (TTMCs), , composite quantum compounds, and single-quintuple-layer Zintl compounds. , Furthermore, materials that exhibit nontrivial phases as a product of functionalization , or substrates effects − have also been theoretically predicted, − but are still in need of experimental investigation. Recently, a study in Zintl materials shows the tunability of topological states driven by alloying with highly magnetic atoms and a magnetic-field-driven changeover from a trivial insulator to a topological material with an applied magnetic field .…”