Comment on “Tunneling-tip-induced collapse of the charge gap in the excitonic insulator Ta2NiSe5”

Abstract

In this study, we investigate the discrepancy between the estimate of Q. He et al. [Phys. Rev. Res. 3, L032074 (2021)], who observed a remarkable collapse of the exciton gap in ${\mathrm{Ta}}_2{\mathrm{NiSe}}_5$ due to the electrostatic field between the scanning tunneling microscope (STM) tip and the sample, and that of a recent angle-resolved photoemission spectroscopy investigation [C. Chen et al., Phys. Rev. Res. 5, 043089 (2023)]. It is proposed that a critical factor contributing to this discrepancy is due to He et al.'s assumption of a constant work function of the STM tip. This assumption led to an underestimation of the tip-induced electric field. Using a literature value for the sample work function, a more substantial electric field strength is obtained, which resolves the apparent conflict between the doping estimates of these two techniques. Furthermore, our findings highlight the importance of the STM tip condition, which can significantly impact the tip work function and, consequently, influence the doping estimation in experiments involving tip-induced electric fields.