The authors report a new class of large-gap quantum spin Hall (QSH) insulators in two-dimensional (2D) transition metal dichalcogenides (TMDCs), specifically MX₂ with M=(Mo, W) and X=(S, Se, Te). These materials exhibit highly tunable topological electronic properties through external electric fields. The study proposes a novel topological field effect transistor (TFET) based on these materials and their van der Waals (vdW) heterostructures. The device demonstrates parametrically enhanced charge-spin conductance through topologically protected transport channels and can be rapidly switched off by electric field through a topological phase transition. This work provides a practical material platform and device architecture for topological quantum electronics, with potential applications in low-power nanoelectronics and topological quantum computing based on Majorana fermions. The discovery of these materials and their properties opens new directions for research and development in both materials science and quantum electronics.The authors report a new class of large-gap quantum spin Hall (QSH) insulators in two-dimensional (2D) transition metal dichalcogenides (TMDCs), specifically MX₂ with M=(Mo, W) and X=(S, Se, Te). These materials exhibit highly tunable topological electronic properties through external electric fields. The study proposes a novel topological field effect transistor (TFET) based on these materials and their van der Waals (vdW) heterostructures. The device demonstrates parametrically enhanced charge-spin conductance through topologically protected transport channels and can be rapidly switched off by electric field through a topological phase transition. This work provides a practical material platform and device architecture for topological quantum electronics, with potential applications in low-power nanoelectronics and topological quantum computing based on Majorana fermions. The discovery of these materials and their properties opens new directions for research and development in both materials science and quantum electronics.