NMR Observation of Rattling Phonons in the Pyrochlore Superconductor KOs2O6

Abstract

We report nuclear magnetic resonance studies on the beta-pyrochlore oxide superconductor KOs2O6. The nuclear relaxation at the K sites is entirely caused by fluctuations of electric field gradient, which we ascribe to highly anharmonic low frequency oscillation (rattling) of K ions. A phenomenological analysis shows a crossover from overdamped to underdamped behavior of the rattling phonons with decreasing temperature and its sudden sharpening below the superconducting transition temperature Tc. Absence of the Hebel-Slichter peak in the relaxation rate at the O sites below Tc also indicates strong electron-phonon coupling.

4 pages, 3 figures

References in corpus (4)

• Mass enhancement, correlations, and strong coupling superconductivity in the beta-pyrochlore KOs2O6
• Thermal Conductivity of the Pyrochlore Superconductor KOs2O6: Strong Electron Correlations and Fully Gapped Superconductivity
• Frustration in Coupled Rattler System: KOs2O6
• Uncommonly High Upper Critical Field in the Superconducting KOs${}_2$O${}_6$ Pyrochlore

Cited by in corpus (12)

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• NMR relaxation and resistivity from rattling phonons in pyrochlore superconductors
• Rattling-Induced Superconductiviy in the Beta-Pyrochlore Oxides AOs2O6
• Electronic texture of the thermoelectric oxide Na0.75CoO2
• Low-lying excitations at the rare-earth site due to rattling motion in the filled skutterudite LaOs_4Sb_{12} revealed by ^{139}La NMR and ^{121/123}Sb NQR
• Superconducting Transition in the $\beta$-Pyrochlore AOs${}_2$O${}_6$ (A=Cs, Rb, K) under Pressure
• A Possible Phase Transition in beta-pyrochlore Compounds
• Vortex Redistribution below the First-Order Transition Temperature in the β-Pyrochlore Superconductor KOs_2O_6
• Theoretical study of NMR relaxation due to rattling phonons
• Magnetic and charge transport properties of the Na-based Os oxide pyrochlore
• Structural and Superconducting Properties of RbOs2O6 Single Crystals
• Green's function of fully anharmonic lattice vibration