ABX6 Monolayers: A new Dirac material family containing high Fermi velocities and topological properties

Dirac materials have received attracting attentions due to their intriguing properties and potential applications in advanced electronics. In this work, we reported 44 new two-dimensional Dirac materials, named ABX6 monolayers, by constructing group IVA, VA, and VIA elements with the same structural prototype. Our first principle calculations revealed that they show excellent dynamical stability, mechanical stability, and thermodynamics stability. Those monolayers possess the elastic constant from 23.93 to 245.57 N/m, attributing to broadly used mechanical strength materials. The electronic calculations show that the Dirac cones in all ABX6 monolayers are both located at K points in Brillouin zone and mainly contributed from the pz orbital of group IVA atoms and group VIA atoms. Their Fermi velocities are from 3.44 × 105 to 6.83 × 105 m/s, which is benefiting for the potential applications in high-speed electric devices. Moreover, it is interesting to notice that the ABX6 monolayers with heavy atoms, such as the ISbSn6 monolayer, exhibit a large band gap of ∼ 0.106 eV, due to the spin-orbital coupling effect. The further calculations reveal their nontrivial topological nature with topological edge states, indicating they could be used as potential dissipationless transport devices at room temperature.