Density Functional Theory of Superconductivity in Doped Tungsten Oxides

Pellegrini C., Glawe H., Sanna A.

II - Fisica della materia
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We apply density functional theory for superconductors (SCDFT) to doped tungsten oxide in three forms: electrostatically doped $WO_3$, perovskite $WO_{3-x}F_{x}$ and hexagonal $Cs_{x}WO_{3}$. We achieve a consistent picture in which the experimental superconducting transition temperature $T_c$ is reproduced, and superconductivity is understood as a weak-coupling state sustained by soft vibrational modes of the $WO_{6}$ octahedra. SCDFT simulations of $Cs_{x}WO_{3}$ allow us to explain the anomalous $T_c$-behavior observed in most tungsten bronzes, where $T_c$ 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 $T_c$ is strongly reduced.

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