Year: 2004
Type: article
Abstract: Electronic, magnetic, and dynamical properties of superconducting $\ensuremath{\beta}$-pyrochlore $\mathrm{K}{\mathrm{Os}}_{2}{\mathrm{O}}_{6}$ and related $\mathrm{Rb}{\mathrm{Os}}_{2}{\mathrm{O}}_{6}$ and $\mathrm{Cs}{\mathrm{Os}}_{2}{\mathrm{O}}_{6}$ compounds are calculated and compared with experiment and contrasted with structurally related spinel pyrochlores. The calculated susceptibility Stoner enhancement (110%) and thermal mass enhancement $\ensuremath{\lambda}=2.5--3$ reflect moderate but perhaps important Coulomb correlations. The ${\mathrm{K}}^{+}$ ion optic mode is found to be unstable, allowing large excursions of $0.5--0.6\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$ from its ideal site of the K ion along ⟨111⟩ directions. This dynamical mode is much less anharmonic in the isostructural Rb and Cs compounds (with larger cations), perhaps accounting for their progressively lower values of ${T}_{c}$. Electron scattering from this very anharmonic mode may be the cause of the anomalous concave-downward resistivity that is seen only in $\mathrm{K}{\mathrm{Os}}_{2}{\mathrm{O}}_{6}$.
Source: Physical Review B
Authors: J. Kuneš, T. Jeong, W. E. Pickett
Language: Latvian
Subfield: Condensed Matter Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2014978335