Realization of monolayer ZrTe5 topological insulators with wide band gaps.

Two-dimensional topological insulators hosting the quantum spin Hall effect have application potential in dissipationless electronics. To observe the quantum spin Hall effect at elevated temperatures, a wide band gap is indispensable to efficiently suppress bulk conduction. Yet, most candidate materials exhibit narrow or even negative band gaps. Here, via elegant control of van der Waals epitaxy, we have successfully grown monolayer ZrTe₅ on a bilayer graphene/SiC substrate. The epitaxial ZrTe₅ monolayer crystalizes in two allotrope isomers with different intralayer alignments of ZrTe₃ prisms. Our scanning tunneling microscopy/spectroscopy characterization unveils an intrinsic full band gap as large as 254 meV and one-dimensional edge states localized along the periphery of the ZrTe₅ monolayer. First-principles calculations further confirm that the large band gap originates from strong spin−orbit coupling, and the edge states are topologically nontrivial. These findings thus provide a highly desirable material platform for the exploration of the high-temperature quantum spin Hall effect.Quantum spin Hall materials hold great potential for future nanoelectronics. Here, authors synthesize a potential host system — monolayer ZrTe₅ — and demonstrate it possesses a band gap wide enough for potential room-temperature applications. [ABSTRACT FROM AUTHOR]