Surface doping manipulation of the insulating ground states in Ta₂Pd₃Te₅ and Ta₂Ni₃Te₅

Manipulating emergent quantum phenomena is a key issue for understanding the underlying physics and contributing to possible applications. Here we study the evolution of insulating ground states of Ta₂Pd₃Te₅ and Ta₂Ni₃Te₅ under in-situ surface potassium deposition via angle-resolved photoemission spectroscopy. Our results confirm the excitonic insulator character of Ta₂Pd₃Te₅. Upon surface doping, the size of its global gap decreases obviously. After a deposition time of more than 7 min, the potassium atoms induce a metal–insulator phase transition and make the system recover to a normal state. In contrast, our results show that the isostructural compound Ta₂Ni₃Te₅ is a conventional insulator. The size of its global gap decreases upon surface doping, but persists positive throughout the doping process. Our results not only confirm the excitonic origin of the band gap in Ta₂Pd₃Te₅, but also offer an effective method for designing functional quantum devices in the future.