Superconducting β(β′)-vanadium bronzes under pressure

Abstract

Since the first superconductivity in vanadium oxides was discovered in β−Na0.33V2O5 under high pressure, β-vanadium bronzes have drawn much interest. In this paper, we report our current high-pressure studies on monovalent β-vanadium bronzes, β−A0.33V2O5 (A=Li, Na, and Ag). The superconducting states are realized by suppressing the charge ordering states under high pressure in all monovalent β-vanadium bronzes, in contrast to divalent β−A0.33V2O5 (A=Ca, Sr, and Pb). The superconducting phases adjacent to the charge ordering phases imply an important role of charge fluctuation for the superconductivity. The obtained pressure-temperature phase diagrams tell us that the superconducting states compete with not only charge ordering states but also new nonsuperconducting metallic states under high pressure. The superconducting states are very sensitive to A-cation nonstoichiometry, suggesting a close relation to the commensurability of carriers and a possibility of non s-wave superconductivity.

Source-reported materials — not catalogue approval

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