Prediction of Large-Gap Topological Insulator in functionalized Ordered Double Transition Metal MXene

Mei-Ling Xu^1*, Zhi-Quan Huang¹, Gennevieve Macam¹, Chia-Hsiu, Hsu¹, Feng-Chuan Chuang¹

¹Department of Physics, National Sun Yat-Sen University, Kaohsiung 804, Taiwan

* Presenter:Mei-Ling Xu, email:b042030009@g-mail.nsysu.edu.tw

MXenes have become popular 2D materials in the recent years owing to the various composition and surface functional possibilities. We study on V₂TiC₂X₂ (X = F, Cl, Br, I, O, H, and OH) using first-principles calculations and find that V₂TiC₂F₂ is a topological insulator. Then, we calculated M₂M’C₂F₂ (M = V, Nb, Ta; M’ = Ti, Zr, Hf ) and found that all of them are topological. Consequently, M₂M’C₂F₂ have band gap at the Γ-point from 40 to 420 meV, sufficiently large for realizing room-temperature quantum spin hall effects. Another advantage of M₂M’C₂O₂ lies in their oxygen covered surfaces which make them antioxidative and stable upon exposure to air. Further analysis in V₂TiC₂F₂ shows that majority of the contribution of band inversion are from the d-orbitals of V atoms. Besides, it remains a robust topology against tensile strain up to 19%. The combined unique property of topological insulators and MXenes make it a valuable 2D material worth of further study with a potential to play an important role in the development of technology.

Keywords: MXene, First-principles calculations, Two-Dimensional materials, Topological Insulator