Extremely strong-coupling superconductivity and anomalous lattice properties in the beta-pyrochlore oxide KOs2O6

Abstract

Superconducting and normal-state properties of the beta-pyrochlore oxide KOs2O6 are studied by means of thermodynamic and transport measurements. It is shown that the superconductivity is of conventional s-wave type and lies in the extremely strong-coupling regime. Specific heat and resistivity measurements reveal that there are characteristic low-energy phonons that give rise to unusual scattering of carriers due to strong electron-phonon interactions. The entity of the low-energy phonons is ascribed to the heavy rattling of the K ion confined in an oversized cage made of OsO6 octahedra. It is suggested that this electron-rattler coupling mediates the Cooper pairing, resulting in the extremely strong-coupling superconductivity.

17 pages (only 4 pages included here. go to http://hiroi.issp.u-tokyo.ac.jp/Published%20papers/K-SC6.pdf for full pages), to be published in PRB

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• Phonon Mode Spectroscopy, Electron-Phonon Coupling and the Metal-Insulator Transition in Quasi-One-Dimensional M2Mo6Se6
• Low-Temperature and High-Energy-Resolution Laser Photoemission Spectroscopy
• Rattling enhanced superconductivity in MV${}_2$Al${}_{20}$ (M = Sc, Lu, Y) intermetallic cage compounds
• On the importance of the electron-phonon coupling function on the superconducting transition temperature in dodecaboride superconductors: A comparison of LuB12 with ZrB12
• Phonon density of states, anharmonicity, electron-phonon coupling and possible multigap superconductivity in the clathrate superconductors Ba8Si46 and Ba24Si100: Why is Tc different in these two compounds?
• Possible Odd-Frequency Superconductivity in Strong-Coupling Electron-Phonon Systems
• Strong Electron-Phonon Coupling Superconductivity Induced by a Low-lying Phonon in IrGe
• Spin-gap opening accompanied by a strong magnetoelastic response in the S=1 magnetic dimer system Ba3BiRu2O9
• NbIr${}_2$B${}_2$ and TaIr${}_2$B${}_2$ -- new low symmetry noncentrosymmetric superconductors with strong spin orbit coupling
• Strong coupling superconductivity mediated by three-dimensional anharmonic phonons
• Rattling and Superconducting Properties of the Cage Compound GaxV2Al20
• Superconducting Transition in the $\beta$-Pyrochlore AOs${}_2$O${}_6$ (A=Cs, Rb, K) under Pressure
• Electron and phonon band-structure calculations for the antipolar SrPt${}_3$P antiperovskite superconductor: Evidence of low-energy two-dimensional phonons
• Superconductivity in an Einstein Solid AxV2Al20 (A = Al and Ga)
• A Possible Phase Transition in beta-pyrochlore Compounds
• Optical conductivity from local anharmonic phonons
• Strong-Coupling Theory of Rattling-Induced Superconductivity
• Unquenched $e_g^1$ orbital moment in the Mott insulating antiferromagnet KOsO4
• Vortex Redistribution below the First-Order Transition Temperature in the β-Pyrochlore Superconductor KOs_2O_6
• Kondo Effect of a Magnetic Ion Vibrating in a Harmonic Potential
• Strong-Coupling Superconductivity in BaPd2As2 Induced by Soft Phonons in the ThCr2Si2-type Polymorph
• Nodeless superconductivity in the cage-type superconductor Sc5Ru6Sn18 with preserved time-reversal symmetry
• Scanning Tunneling Spectroscopy in the Superconducting State and Vortex Cores of the beta-pyrochlore KOs2O6
• Theoretical study of NMR relaxation due to rattling phonons
• Observation of Low-Energy Einstein Phonon and Superconductivity in Single-Crystalline LaBe${}_{13}$
• Phonon Dynamics and Multipolar Isomorphic Transition in beta-pyrochlore KOs2O6
• Structural and Superconducting Properties of RbOs2O6 Single Crystals
• Heavy-Electron Formation and Bipolaronic Transition in the Anharmonic Holstein Model
• Magnetic and charge transport properties of the Na-based Os oxide pyrochlore
• Superconductivity of centrosymmetric and non-centrosymmetric phases in antiperovskite (Ca,Sr)Pd${}_3$P
• Electrical and Thermal Transport Properties of the beta-Pyrochlore Oxide CsW2O6
• Green's function of fully anharmonic lattice vibration
• Ab initio study on magnetism suppression, anharmonicity, rattling mode and superconductivity in Sc${}_{6}M$Te${}_2$ ($M$=Fe, Co, Ni)
• Superconductivity in Nb5Ir3-xPtxO
• Large and homogeneous mass enhancement in the rattling-induced superconductor KOs${}_2$O${}_6$
• Superconducting and Structural Transitions in the β-Pyrochlore Oxide KOs2O6 under High Pressure
• Anharmonic effects in magnetoelastic chains
• Upper critical field and de Haas-van Alphen oscillations in KOs${}_2$O${}_6$ measured in a hybrid magnet
• Superconductivity and Rattling under High Pressure in the beta-Pyrochlore Oxide RbOs2O6
• Partial order in a frustrated Potts model
• Anomalous Isotope Effect in Rattling-Induced Superconductor