Revealing the Role of Hydrogen in Electron-Doping Mottronics for Strongly Correlated Vanadium Dioxide.

Hydrogen-associated electron-doping Mottronics for d-band correlated oxides (e.g., VO) opens up a new paradigm to regulate the electronic functionality via directly manipulating the orbital configuration and occupancy. Nevertheless, the role of hydrogen in the Mottronic transition of VO is yet unclear because opposite orbital reconfigurations toward either the metallic or highly insulating states were both reported. Herein, we demonstrate the root cause for such hydrogen-induced multiple electronic phase transitions by H quantification using nuclear reaction analysis. A low hydrogenation temperature is demonstrated to be vital in achieving a large hydrogen concentration ( ≈ 10 cm) that further enhances the t orbital occupancy to trigger electron localizations. In contrast, elevating the hydrogenation temperatures surprisingly reduces to ∼10 cm but forms more stable metallic HVO. This leads to the recognition of a weaker hydrogen interaction that triggers electron localization within VO via Mottronically enhancing the orbital occupancies.