Robustness of Excitonic Coupling in Ta2NiSe5 Against Electronic Inhomogeneity Introduced by S Substitution for Se

Electronic properties of various insulators can be controlled by chemical substitution. For example, exotic superconducting phases are often obtained by chemical substitution in Mott insulators. Compared to Mott insulators, impact of chemical substitution on excitonic insulators is not well explored yet. In the present work, space-resolved angle-resolved photoemission spectroscopy of the model Ta2Ni(Se1-xSx)(5) is reported in which S substitution for Se is used to control the excitonic behavior. The substitution introduces electronic inhomogeneity with the Se 4p/S 3p valence band exhibiting strong position dependence. In contrast, the flat top valence band, which is a signature of the excitonic insulating phase, does not show any appreciable position dependence except the effect of surface corrugation. This indicates that the excitonic coupling in Ta2NiSe5 is robust against the electronic inhomogeneity induced by the S substitution.

Automated summary

The electronic properties of insulators can be controlled by chemical substitution, which has been used to obtain exotic superconducting phases in Mott insulators. However, the impact of chemical substitution on excitonic insulators is not well studied. In this study, space-resolved angle-resolved photoemission spectroscopy of Ta2Ni(Se1-xSx)(5) was conducted to explore the effect of S substitution on the excitonic behavior. The results showed that the substitution introduced electronic inhomogeneity, but the excitonic coupling in Ta2NiSe5 remained robust against this inhomogeneity.