Oxidation-Induced Topological Phase Transition in Monolayer 1T'-WTe2.

Monolayer (ML) tungsten ditelluride (WTe2) is a well-known quantum spin Hall (QSH) insulator with topologically protected gapless edge states, thus promising dissipationless electronic devices. However, experimental findings exhibit the fast oxidation of ML WTe2 in ambient conditions. To reveal the changes of topological properties of WTe2 arising from oxidation, we systematically study the surface oxidation reaction of ML 1T'-WTe2 using first-principles calculations. The calculated results indicate that the fast oxidation of WTe2 originates from the existence of H2O in air, which significantly promotes the oxidation of ML 1T'-WTe2. More importantly, this low-coverage oxidized WTe2 loses its topological features and is changed into a trivial insulator. Furthermore, we propose a fully oxidized ML WTe2 that can still possess the QSH insulator states. The topological phase transition induced by oxidation provides exotic insight into understanding the topological features of layered transition-metal dichalcogenide materials.