Hydrogen-Associated Filling-Controlled Mottronics Within Thermodynamically Metastable Vanadium Dioxide.

Abstract

The discovery of hydrogen-associated topotactic phase modulations in correlated oxide system has emerged as a promising paradigm to explore exotic electronic states and physical functionality. Here hydrogen-induced Mott phase transitions are demonstrated for metastable VO₂ (B) toward new electron-itinerant hydrogenated phases via introducing non-equilibrium condition, delicately delivering a rich spectrum of hydrogen-associated electronic states. Of particular interest, the highly robust but reversible hydrogenated phase achievable in metastable VO₂ (B) significantly benefits protonic device applications, which is in contrast with well-known VO₂ (M1), where the metallic hydrogenated phase readily turns into insulating state with extensive hydrogen doping. Establishing correlated VO₂ at metastable status fundamentally surpasses the thermodynamic restrictions to expand the adjustability in their electronic structure, giving rise to new electronic states and a superior resistive switching of 10²-10⁵ to the counterparts in widely-reported VO₂ (M1). Utilizing the theoretical calculations and synchrotron radiation analysis, the hydrogen-associated phase modulation in metastable VO₂ (B) is dominantly driven by band-filling-controlled orbital reconfiguration, while the concurrent structural evolution unveils a strong ion-electron-lattice coupling. The present work provides fundamentally new tuning knob for adjusting the energy landscape of electron-correlated system, advancing the rational design of unachievable electronic states in hydrogen-related equilibrium phase diagram.