Frustration in the coupled rattler system KOs2O6
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چکیده
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 and CsOs2O6 arise from the relative weakness of intersite coupling, which is related to limited space for rattling in the latter compounds. We argue that the unusual physical properties of KOs2O6 are related to unconventional lattice dynamics rather than electronic correlations.
منابع مشابه
KOs2O6: Superconducting rattler
Electronic structure calculations and experimental data point to soft local vibrations of alkali ions in AOs2O6 (A 1⁄4 K, Rb, Cs). Due to its size the potassium ion experiences an extremely anharmonic and broad potential well. We use ab initio energies and forces to derive the Hamiltonian for the dynamics of K ions and solve the single site problem. r 2006 Published by Elsevier B.V.
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تاریخ انتشار 2006