Oxidation-Induced Topological Phase Transition in Monolayer 1T′-WTe₂

Abstract

Monolayer (ML) tungsten ditelluride (WTe) 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 WTe in ambient conditions. To reveal the changes of topological properties of WTe arising from oxidation, we systematically study the surface oxidation reaction of ML 1T'-WTe using first-principles calculations. The calculated results indicate that the fast oxidation of WTe originates from the existence of HO in air, which significantly promotes the oxidation of ML 1T'-WTe. More importantly, this low-coverage oxidized WTe loses its topological features and is changed into a trivial insulator. Furthermore, we propose a fully oxidized ML WTe 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.

Origin of Two-Dimensional Vertical Ferroelectricity in WTe2 Bilayer and Multilayer

“…A very recent study further demonstrated the out-of-plane switchable polarization in two- or three-layer WTe 2 , although WTe 2 is well-known as a topological semimetal in previous reports. − Despite the polarization that was almost negligible compared with traditional perovskite FE (3 orders of magnitude lower than BaTiO 3 ), the Curie temperature amazingly turned out to be around 350 K. The origin of such FE is still unclarified, as the vertical polarization seems to be switchable without vertical ion displacement. It was supposed in this report that the FE may origin from the electron–hole correlation rather than lattice instability, where a relative motion of the electron cloud relative to the ion core may take place .…”

Strain-Controllable Phase and Magnetism Transitions in Re-Doped MoTe2 Monolayer

“…24 Particularly, 1T′-WTe 2 is even more stable than the 2H phase. 25 Various methods have been applied to tune the transition barrier between these three phases to satisfy diverse needs in multiple devices. For example, Wang et al systematically investigated the electro-chemical dynamic process of MoS 2 nanosheets upon lithium intercalation by in situ high-resolution transmission electron microscopy.…”

Surface band bending in semimetal Td-WTe2

“…According to XPS measurements, 22,23,26−28 the oxidation driving force are formation of WO x and TeO x on the surface of WTe 2 . Theoretical calculation 24,29 claimed the fast oxidation happens with the aid of H 2 O, which can decrease the reaction barrier. And charge depletion was found to near the O adsorption site, which may induce charge dipolar and even polarization.…”