Surface Doping and Dual Nature of the Band Gap in Excitonic Insulator Ta₂NiSe₅.

ABSTRACT: Excitons in semiconductors and molecules are widely utilized in photovoltaics and optoelectronics, and high-temperature coherent quantum states of excitons can be realized in artificial electron-hole bilayers and an exotic material of an excitonic insulator (EI). Here, we investigate the band gap evolution of a putative high-temperature EI Ta₂NiSe₅ upon surface doing by alkali adsorbates with angle-resolved photoemission and density functional theory (DFT) calculations. The conduction band of Ta₂NiSe₅ is filled by the charge transfer from alkali adsorbates, and the band gap decreases drastically upon the increase of metallic electron density. Our DFT calculation, however, reveals that there exist both structural and excitonic contributions to the

SUBMITTER: Lee S 

PROVIDER: S-EPMC11394347 | biostudies-literature | 2024 Sep

REPOSITORIES: biostudies-literature