Predicting Two-Dimensional Topological Insulators upon Substitutional Doping in Monolayer Transition Metal Dichalcogenides

Zhi-Quan Huang¹, Rovi Angelo B. Villaos¹, Chia-Hsiu Hsu¹, Liang-Ying Feng¹, Feng-Chuan Chuang¹, Emmanuel Florido², Hsin Lin³, Aniceto Maghirang^1*

¹Physics, National Sun Yat-Sen University, Kaohsiung City, Taiwan
²Institute of Mathematical Sciences and Physics, University of the Philippines Los Baños, Los Baños City, Philippines
³Institute of Physics, Academia Sinica, Taipei City, Taiwan

* Presenter:Aniceto Maghirang, email:maggiemaghirang@gmail.com

Substitutional doping of two-dimensional transition metal dichalcogenides (TMDs) is of importance in tuning and possible enhancement of its electronic, physical and chemical properties for vast industrial applications. Here we report a systematic first-principles study of possible 2D topological insulator phases, also known as quantum spin Hall (QSH) insulator, upon halogen (Cl, Br, or I) or pnictogen (P, As, Sb, or Bi) substitution of monolayer MX2(M=V, Nb, Ta, Tc, or Re; X=S, Se, or Te), including the effects of one-sided hydrogen adsorption, for both 1T and 2H crystal structures. For group VB, a structural phase transition, from 2H to 1T, was observed for all the pnictogen substitution while no structural phase transition upon halogen substitution or hydrogen adsorption. Nontrivial phases were obtained upon pnictogen substitution of group VB while trivial phases upon halogen substitution and hydrogen adsorption. For group VIIB, structural phase transition, from 2H to 1T, was observed for all the halogen substitution or hydrogen adsorption while no structural phase transition upon pnictogen substitution. Nontrivial phases were obtained upon halogen substitution or hydrogen adsorption of group VIIB while trivial phases upon pnictogen substitution. The topology of some transition metal dichalcogenides (TMDs) becomes nontrivial upon pnictogen substitution of group VB and halogen substitution or hydrogen adsorption of group VIIB, demonstrating its suitability for synthesis on various substrates.

Keywords: 2D topological insulators, topological phase transition, quantum spin Hall effect, transition metal dichalcogenide thin films, electronic structures, first-principles calculations