Robust Excitonic‐Insulating States in Cu‐Substituted Ta ₂ NiSe ₅

Excitonic insulators exhibit intriguing quantum phases that further attract numerous interests in engineering the electrical and optical properties of Ta2NiSe5. However, tuning electronic such as spin-orbit coupling strength orbital repulsion via pressure Ta2NiSe5 are always accompanied with electron-hole pair breaking, which is a bottleneck for applications. Here, robust excitonic-insulating states invariant electron-doping concentrations demonstrated. The electron doping conducted by substituting Cu into Ni site (Ta2Ni1-xCuxSe5). majority carrier pristine sample hole-type converted to electron-type concentration over x = 0.01, whose density can be controlled varying concentration. excitonic transition temperature (Tc) does not significantly alter concentrations, stark contrast declining Tc dopant Fe or Co increases. conductivity data also demonstrate Cu-doped findings n-type Cu-substituted utilized device applications using excitons.