Unraveling the Atomic-Scale Lattice Distortion and Selective Electronic Orbital Filling During the Hydrogen Induced...

Clarifying the lattice-charge coupling and resultant electronic phase transition in correlated materials is important for understanding the underlying physics and emergent properties. Ionic intercalation, along with the accompanying charge doping, can trigger the coupling between the lattice and charge degrees of freedom, and provides us a powerful approach to investigate this research focus. Here, with vanadium oxide (VO₂) as a model system, the proton-induced crystal lattice and orbital variations are experimentally and theoretically revealed, which collaboratively modulate the electronic state and closely related insulator-metal-insulator transitions. First, the atomic-scale anti-phase VO₆ octahedra rotation induced by the intercalated protons is directly observed, which causes the dimerization of vanadium atoms. Meanwhile, the synergistically doped electrons selectively control the orbital-resolved filling. Second, following the first-principles calculations, the separate roles of lattice distortion and electron doping in the orbital occupation at the Fermi level are further elucidated. Finally, the comprehensive electronic phase diagram with the dependence of VO₆ octahedra rotation angle and electronic doping level is mapped. These results greatly deepen the understanding of the metal-insulator transitions in correlated materials, and provide guidelines to design other novel functionalities.