Surface reconstructions and electronic structure of metallic delafossite thin films*

Motivated by the potential to create electronic and magnetic characteristics that are not accessible in bulk systems, the study of low-dimensional metallic delafossites with the general chemical formula ABO2 is gaining popularity. Understanding the surface behavior of the delafossite compounds is crucial due to their distinct layer structure, which gives rise to diverse surface states, electronic reconstructions, and surface reconstructions. We study epitaxial PtCoO₂, PdCoO₂, and PdCrO₂ films by combining molecular-beam epitaxy and angle-resolved photoemission spectroscopy. Through precise control of surface termination and treatment, we observed distinct surface reconstructions on the PtCoO₂ films, PdCoO₂ films, and PdCrO₂ films. Notably, these reconstructions have not been reported in prior studies of delafossites. Furthermore, our computational analysis reveals the relative stability of the BO₂ surface and the significant reduction in surface formation energy achievable through reconstruction on the A-terminated surface. These experimental and theoretical insights shed light on the surface phenomena occurring in metallic delafossites, paving the way to exploring their distinctive properties in low-dimensional studies.