Density functional theory of superconductivity in doped tungsten oxides

We apply density functional theory for superconductors (SCDFT) to doped tungsten oxide in three forms: electrostatically doped WO3, perovskite WO3−xFx, and hexagonal CsxWO3. We achieve a consistent picture in which the experimental superconducting transition temperature Tc is reproduced, and superconductivity is understood as a weak-coupling state sustained by soft vibrational modes of the WO6 octahedra. SCDFT simulations of CsxWO3 allow us to explain the anomalous Tc behavior observed in most tungsten bronzes, where Tc decreases with increasing carrier density. Here, the opening of structural channels to host Cs atoms induces a softening of strongly coupled W-O modes. By increasing the Cs content, these modes are screened and Tc is strongly reduced