Ternary vanadium oxide bronzes (MxV2O5), a singularly unique class of oxides that exist for a large number of known metal intercalants (M), exhibits a variety of sharply nonlinear electronic phenomena including charge and spin density waves, metal-insulator transitions, and superconductivity, arising in part from the rich redox chemistry of vanadium and the ability to readily localize/delocalize charge density. We have previously reported that β′-CuxV2O5 exhibits a metal-insulator transition around 300 K, but have observed that the metal-insulator transition in single nanowires is extremely sensitive to copper stoichiometry, x (β′-CuxV2O5). The β/β′ phase is a pseudo 1D tunnel structure in which the metal cation, in this case, Cu (I) resides within the tunnel and partially reduces specific V5+ sites in the V2O5 framework to V4+, resulting in charge ordered networks. First-principles density functional theory calculations, photoemission spectroscopy, and single crystal diffraction have been used to probe the mechanistic underpinnings for the metal-insulator transition. We have predicted that the melting of the polaronic state because of subtle perturbations in the position of the copper ions results in the delocalization of the electrons in the charge ordered network, ultimately manifesting in metallic behavior. Insights into the structural and electronic properties underpinning this transition obtained during this study will allow for rational tuning of transition temperature and magnitude (by changing x) and help to establish the structure-function relationship in this material.

Mapping polaronic distortions across the metal-insulator transition of nanoscale β′-CuxV2O5

2019 Spring National Meeting

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