Quantum Spin Hall Effects in Van der Waals Materials

The quantum spin Hall (QSH) effect, first predicted in graphene by Kane and Mele in 2004, has become a key platform for exploring spin–orbit coupling, topology, and electronic interactions. Initially demonstrated in quantum wells, the field has expanded with the emergence of van der Waals (vdW) materials. This review focuses on vdW systems, which provide unique advantages: exposed surfaces allow comprehensive spectroscopic and microscopic detection of the QSH state; mechanical stacking enables symmetry tuning and proximity effects; and moiré engineering introduces new topology and strong correlations. We highlight two monolayer families, 1T'-MX₂ and (Formula presented.), represented by WTe₂ and TaIrTe₄, respectively, which host QSH phases in close proximity to other quantum states including excitonic insulators, charge density waves, and superconductivity. Their low symmetry and topology produce rich quantum geometrical responses, from nonlinear Hall to circular photogalvanic effects. We also discuss moiré systems that combine topology with flatband physics, enabling spontaneous symmetry breaking and transitions from QSH to quantum anomalous Hall (QAH) states. Recent observations of fractionalized QAH and QSH states mark a major advance in condensed matter physics. Finally, we outline potential applications, such as nonlinear Hall–based microwave rectification and fractional states for topological quantum computing.