Pressure-Induced Intermetallic Charge Transfer and Semiconductor-Metal Transition in Two-Dimensional AgRuO3

The intricate correlation between charge degrees of freedom and physical properties is a fascinating area of research in solid state chemistry and condensed matter physics. Herein, we report on the pressure-induced successive charge transfer and accompanied resistive evolution in honeycomb layered ruthenate AgRuO3. Structural revisiting and spectroscopic analyses affirm the ilmenite type R-3 structure with mixed valence cations as Ag+1/+2Ru+4/+5O3 at ambient pressure. In-situ pressure- and temperature-dependent resistance variation reveals a successive insulator-metal-insulator transition upon pressing, accompanied by unprecedented charge transfer between Ag and Ru under applied pressure, and a further structural phase transition in the insulator region at higher pressure. These phenomena are also corroborated by in-situ pressure-dependent Raman spectra, synchrotron X-ray diffraction, bond valence sums, and electronic structure calculations, emphasizing the dominated rare Ag2+, and near zero thermal expansion in the ab-plane in the metallic zone mostly due to the Jahn-Teller effect of d(9)-Ag2+. The multiple electronic instabilities in AgRuO3 may offer new possibilities toward novel and unconventionally physical and chemical behaviors in strongly correlated honeycomb lattices. [GRAPHICS]