Structural, vibrational and electronic properties of the superconductor CuxTiSe2: theoretical and experimental insights

Abstract

The crystal/electronic structure and vibrational properties of the Cu_xTiSe₂ intercalation compounds were studied combining experimental and theoretical techniques. The Cu added into the TiSe₂ matrix was characterized as an intercalant atom into van der Waals gaps from Raman spectroscopy analysis. Theoretical and experimental data indicate the Cu-intercalation effect on the crystalline structure as a local disorder affecting [TiSe₆] clusters from Se⋯Se layers, which results in a volume expansion. A significant charge transfer from Cu atoms to the host lattice results in a change from Ti⁴⁺ to Ti³⁺ species, narrowing the band-gap and increasing the superconductivity of the material.