This study reports a new class of large-gap quantum spin Hall (QSH) insulators in two-dimensional transition metal dichalcogenides (TMDCs), specifically MX₂ with M = (Mo, W) and X = (S, Se, Te). These materials exhibit tunable topological electronic properties through external electric fields. The researchers propose a novel topological field effect transistor (TFET) based on these materials and their van der Waals heterostructures. The device demonstrates enhanced charge-spin conductance through topologically protected transport channels and can be rapidly switched off via topological phase transition by applying an electric field, without relying on carrier depletion. This work provides a practical platform and device architecture for topological quantum electronics. The discovery of graphene has spurred extensive research into two-dimensional (2D) materials, revealing their unique properties and functionalities. 2D materials can be horizontally patterned using chemical and mechanical techniques, and their weak van der Waals interactions allow for vertical stacking, forming van der Waals heterostructures. However, the vast family of 2D materials and their heterostructures have been underexploited for topological phases, particularly QSH insulators. QSH insulators have insulating bulk but conducting edge states protected by time-reversal symmetry. While QSH-based devices could offer low-dissipation quantum electronics, their practical implementation is hindered by small band gaps, limited conducting channels, and lack of efficient switching methods. The study shows that 2D materials offer a practical platform to overcome these challenges. Using first-principles calculations, the researchers find a new class of large-gap QSH insulators in 2D TMDCs. They demonstrate the possibility of a novel van der Waals heterostructured topological field effect transistor (vdW-TFET) made of 2D atomic layer materials. The device exhibits enhanced conductance through QSH edge channels and can be rapidly switched off via topological phase transition by applying an electric field. The electronic structures of 1T'-MX₂ were calculated using many-body perturbation theory within the GW approximation. The 1T'-MoS₂ is a semiconductor with a fundamental gap of about 0.1 eV, and the Z₂ band topology was determined by the parity of valence bands at time-reversal invariant momenta. The study also shows that other 1T'-MX₂ materials have nontrivial Z₂ band topology due to p-d band inversion. The QSH insulator phase in 2D 1T'-MX₂ leads to helical edge states protected by time-reversal symmetry. The researchers demonstrated these edge states using iterative Green's function calculations. The ability to control topological electronic properties is crucial for device applications. The study shows that a vertical electric field can control the electronic structure of 1T'-MoS₂ QSH insulator, inducing a topological phase transition. This enables all-electThis study reports a new class of large-gap quantum spin Hall (QSH) insulators in two-dimensional transition metal dichalcogenides (TMDCs), specifically MX₂ with M = (Mo, W) and X = (S, Se, Te). These materials exhibit tunable topological electronic properties through external electric fields. The researchers propose a novel topological field effect transistor (TFET) based on these materials and their van der Waals heterostructures. The device demonstrates enhanced charge-spin conductance through topologically protected transport channels and can be rapidly switched off via topological phase transition by applying an electric field, without relying on carrier depletion. This work provides a practical platform and device architecture for topological quantum electronics. The discovery of graphene has spurred extensive research into two-dimensional (2D) materials, revealing their unique properties and functionalities. 2D materials can be horizontally patterned using chemical and mechanical techniques, and their weak van der Waals interactions allow for vertical stacking, forming van der Waals heterostructures. However, the vast family of 2D materials and their heterostructures have been underexploited for topological phases, particularly QSH insulators. QSH insulators have insulating bulk but conducting edge states protected by time-reversal symmetry. While QSH-based devices could offer low-dissipation quantum electronics, their practical implementation is hindered by small band gaps, limited conducting channels, and lack of efficient switching methods. The study shows that 2D materials offer a practical platform to overcome these challenges. Using first-principles calculations, the researchers find a new class of large-gap QSH insulators in 2D TMDCs. They demonstrate the possibility of a novel van der Waals heterostructured topological field effect transistor (vdW-TFET) made of 2D atomic layer materials. The device exhibits enhanced conductance through QSH edge channels and can be rapidly switched off via topological phase transition by applying an electric field. The electronic structures of 1T'-MX₂ were calculated using many-body perturbation theory within the GW approximation. The 1T'-MoS₂ is a semiconductor with a fundamental gap of about 0.1 eV, and the Z₂ band topology was determined by the parity of valence bands at time-reversal invariant momenta. The study also shows that other 1T'-MX₂ materials have nontrivial Z₂ band topology due to p-d band inversion. The QSH insulator phase in 2D 1T'-MX₂ leads to helical edge states protected by time-reversal symmetry. The researchers demonstrated these edge states using iterative Green's function calculations. The ability to control topological electronic properties is crucial for device applications. The study shows that a vertical electric field can control the electronic structure of 1T'-MoS₂ QSH insulator, inducing a topological phase transition. This enables all-elect