Anomalous Isotope Effect in Rattling-Induced Superconductor

Abstract

In order to clarify that the Cooper pair in $\beta$-pyrochlore oxides is mediated by anharmonic oscillation of guest atom, i.e., rattling, we propose an experiment to detect anomalous isotope effect. In the formula of $T_{\mathrm{c}}\propto M^{-\eta }$, where $T_{\mathrm{c}}$ is superconducting transition temperature and $M$ denotes mass of the oscillator, it is found that the exponent $\eta$ is increased with the increase of anharmonicity of a potential for the guest atom. We predict that $\eta$ becomes larger than 1/2 in rattling-induced superconductor, in sharp contrast to $\eta =1/2$ for weak-coupling superconductivity due to harmonic phonons and $\eta <1/2$ for strong-coupling superconductivity with the inclusion of the effect of Coulomb interaction.

7 pages, 5 figures. Submitted to J. Phys. Soc. Jpn

References in corpus (8)

• Extremely strong-coupling superconductivity and anomalous lattice properties in the beta-pyrochlore oxide KOs2O6
• Orbital ordering phenomena in $d$- and $f$-electron systems
• Rattling-Induced Superconductiviy in the Beta-Pyrochlore Oxides AOs2O6
• Mass enhancement, correlations, and strong coupling superconductivity in the beta-pyrochlore KOs2O6
• Strong-Coupling Theory of Rattling-Induced Superconductivity
• Electron Mass Enhancement due to Anharmonic Local Phonons
• Phonon Dynamics and Multipolar Isomorphic Transition in beta-pyrochlore KOs2O6
• Large and homogeneous mass enhancement in the rattling-induced superconductor KOs${}_2$O${}_6$

Cited by in corpus (1)

• Rattling enhanced superconductivity in MV${}_2$Al${}_{20}$ (M = Sc, Lu, Y) intermetallic cage compounds