Topology and Correlations in Thin-Layered TaIrTe₄

I will present experimental studies on the topological and correlated properties of monolayer TaIrTe₄. First, I will discuss a dual quantum spin Hall (QSH) insulator, arising from the interplay between its single-particle topology and density-tuned correlations. At charge neutrality, monolayer TaIrTe₄ exhibits QSH insulator behavior, characterized by enhanced nonlocal transport and quantized helical edge conductance. Upon introducing electrons from charge neutrality, TaIrTe₄ only shows metallic behavior in a small range of charge densities but quickly goes into a new insulating state. This insulating state could arise from a strong electronic instability near the van Hove singularities, likely leading to a charge density wave. Within this correlated insulating gap, we observe a resurgence of the QSH state. If time permits, I will also discuss our recent efforts to study this correlated gap using nonlinear Hall responses.