The discovery of filling-controlled phase modulations in correlated systems opens an emerging paradigm to unlock unique electromagnetic states and physical phenomena, transcending traditional paradigms. Here, correlated VO₂ (B) is selected as a model system to realize multiple electronic phase modulations through ionic evolution, leveraging the inherent V₄O₁₀-type double-layered structure and thermodynamic metastability. The introduction of electron carriers into the V-3d orbital of metastable VO₂ (B), as driven by W^6+ substitution, oxygen deficiency, or protonation, triggers the carrier delocalization, giving rise to sequential electronic phase modulations, beyond well-established M1 and R phases of VO₂. Of particular note is the synergistic interplay between oxygen defects and interstitial protons in cooperatively driving electronic state evolutions in VO₂ (B) through band-filling regulation, enabling the robust control over the energy landscape in a reversible pathway. Utilizing synchrotron-related spectroscopy techniques and theoretical calculations, we reveal that the band filling in low-energy ^* orbital of VO₂ (B) through electron doping governs electronic phase modulations, delivering a unified physical picture. Our findings not only demonstrate a powerful tuning knob for adjusting correlated electronic states in metastable layered-structure materials, fostering exotic physical functionalities and phenomena but also extend the horizons in materials designs for iontronic device applications.
Zhou et al. (Mon,) studied this question.