A Possible Phase Transition in beta-pyrochlore Compounds

Abstract

We investigate a lattice of interacting anharmonic oscillators by using a mean field theory and exact diagonalization. We construct an effective five-state hopping model with intersite repulsions as a model for beta-pyrochlore AOs_2O_6(A=K, Rb or Cs). We obtain the first order phase transition line from large to small oscillation amplitude phases as temperature decreases. We also discuss the possibility of a phase with local electric polarizations. Our theory can explain the origin of the mysterious first order transition in KOs_2O_6.

4 pages, 4 figures, submitted to J. Phys. Soc. Jpn

References in corpus (14)

• Extremely strong-coupling superconductivity and anomalous lattice properties in the beta-pyrochlore oxide KOs2O6
• Crystal structure of the pyrochlore oxide superconductor KOs${}_2$O${}_6$
• NMR relaxation and resistivity from rattling phonons in pyrochlore superconductors
• Correlation Effects and Structural Dynamics in the $\beta$-Pyrochlore Superconductor KOs${}_2$O${}_6$
• Mass enhancement, correlations, and strong coupling superconductivity in the beta-pyrochlore KOs2O6
• Second Anomaly in the Specific Heat of beta-Pyrochlore Oxide Superconductor KOs2O6
• NMR Observation of Rattling Phonons in the Pyrochlore Superconductor KOs2O6
• Thermal Conductivity of the Pyrochlore Superconductor KOs2O6: Strong Electron Correlations and Fully Gapped Superconductivity
• Frustration in Coupled Rattler System: KOs2O6
• Effects of Rattling Phonons on the Quasiparticle Excitation and Dynamics in the Superconducting $\beta$-Pyrochlore KOs${}_2$O${}_6$
• Evidence for s-wave superconductivity in the new beta-pyrochlore oxide RbOs2O6
• Neutron Scattering Study of the Localized Mode in the beta-Pyrochlore Superconductors AOs2O6
• Superconducting Transition in the $\beta$-Pyrochlore AOs${}_2$O${}_6$ (A=Cs, Rb, K) under Pressure
• Theory of Ultrasonic Dispersion in Local Phonon Systems Coupled with Conduction Electrons

Cited by in corpus (8)

• Rattling enhanced superconductivity in MV${}_2$Al${}_{20}$ (M = Sc, Lu, Y) intermetallic cage compounds
• Strong coupling superconductivity mediated by three-dimensional anharmonic phonons
• Strong-Coupling Theory of Rattling-Induced Superconductivity
• First Order Bipolaronic Transition at Finite Temperature in the Holstein Model
• Kondo Effect of a Magnetic Ion Vibrating in a Harmonic Potential
• Phonon Dynamics and Multipolar Isomorphic Transition in beta-pyrochlore KOs2O6
• Heavy-Electron Formation and Bipolaronic Transition in the Anharmonic Holstein Model
• Superconducting and Structural Transitions in the β-Pyrochlore Oxide KOs2O6 under High Pressure