Authors: Christopher C. Leon, Abhishek Grewal, Klaus Kuhnke, Klaus Kern, Olle Gunnarsson
Published: 2022-02-21
DOI: 10.1038/s41467-022-28392-8
Source: Full article
AbstractThe alkali halides are ionic compounds. Each alkali atom donates an electron to a halogen atom, leading to ions with full shells. The valence band is mainly located on halogen atoms, while, in a traditional picture, the conduction band is mainly located on alkali atoms. Scanning tunnelling microscopy of NaCl at 4 K actually shows that the conduction band is located on Cl− because the strong Madelung potential reverses the order of the Na+ 3s and Cl− 4s levels. We verify this reversal is true for both atomically thin and bulk NaCl, and discuss implications for II-VI and I-VII compounds.