Large and homogeneous mass enhancement in the rattling-induced superconductor KOs2O6

Effects of Rattling Phonons on the Dynamics of Quasiparticle Excitation in the -Pyrochlore KOs2O6 Superconductor

Novel vortex distribution in the β-pyrochlore superconductor KOs2O6

By utilizing the micro-Hall probe array, we study the superconducting and the vortex states in a single crystal of KOs2O6 near the first-order transition at Tp ∼ 8 K, which is associated with a change in the rattling motion of K ions. We show that below the first-order transition, the lower critical field exhibits a distinct decrease, suggesting that the electron-phonon coupling is weakened bel...

Correlation effects and structural dynamics in the b-pyrochlore superconductor KOs2O6

Electronic, magnetic, and dynamical properties of superconducting b-pyrochlore KOs2O6 and related RbOs2O6 and CsOs2O6 compounds are calculated and compared with experiment and contrasted with structurally related spinel pyrochlores. The calculated susceptibility Stoner enhancement (110%) and thermal mass enhancement l=2.5–3 reflect moderate but perhaps important Coulomb correlations. The K+ ion...

Frustration in the coupled rattler system KOs2O6

Starting from ab initio electronic structure results we study dynamics of potassium ions in the pyrochlore superconductor KOs2O6. An effective ionic Hamiltonian characterized by an on-site instability rattler and frustrated nearest-neighbor interaction is derived and various approximations are investigated. We show that qualitative differences in the properties of KOs2O6 and its analogs RbOs2O6...

Angle-resolved photoemission spectroscopy of the antiferromagnetic superconductor Nd1.87Ce0.13CuO4: anisotropic spin-correlation gap, pseudogap, and the induced quasiparticle mass enhancement.

We performed high-resolution angle-resolved photoemission spectroscopy on Nd1.87Ce0.13CuO4, which is located at the boundary of the antiferromagnetic (AF) and the superconducting phase. We observed that the quasiparticle (QP) effective mass around (pi,0) is strongly enhanced due to the opening of the AF gap. The QP mass and the AF gap are found to be anisotropic, with the largest value near the...