Correlation Effects and Structural Dynamics in the $β$-Pyrochlore Superconductor KOs$_{2}$O$_{6}$

J. Kunes; T. Jeong; W. E. Pickett

doi:10.1103/PhysRevB.70.174510

paper

Correlation Effects and Structural Dynamics in the $β$ -Pyrochlore Superconductor KOs $_{2}$ O $_{6}$

arXiv:cond-mat/0412031 · doi:10.1103/PhysRevB.70.174510

Abstract

Electronic, magnetic, and dynamical properties of the new superconducting $β$ -pyrochlore KOs $_{2}$ O $_{6}$ and related RbOs $_{2}$ O $_{6}$ and CsOs $_{2}$ 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 $λ$ = 2.5-3 reflect moderate but perhaps important Coulomb correlations. The K $^{+}$ ion optic mode is found to be unstable, allowing large excursions of 0.5-0.6 Åfrom 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 KOs $_{2}$ O $_{6}$ .

6 pages, 8 figures

Correlation Effects and Structural Dynamics in the β-Pyrochlore Superconductor KOs2​O6​

Abstract

Correlation Effects and Structural Dynamics in the $β$ -Pyrochlore Superconductor KOs $_{2}$ O $_{6}$