Quantum spin Hall state in monolayer 1T-TMDCs.

Although the 1Tphase is rare in the transition metal dichalcogenides (TMDCs) family, it has attracted rapid growing research interest due to the coexistence of superconductivity, unsaturated magneto-resistance, topological phases etc. Among them, the quantum spin Hall (QSH) state in monolayer 1T-TMDCs is especially interesting because of its unique van der Waals crystal structure, bringing advantages in the fundamental research and application. For example, the van der Waals two-dimensional (2D) layer is vital in building novel functional vertical heterostructure. The monolayer 1T-TMDCs has become one of the widely studied QSH insulator. In this review, we review the recent progress in fabrications of monolayer 1T-TMDCs and evidence that establishes it as QSH insulator.