Ferromagnetism in the Mott Insulator Ba2NaOsO6

Results are presented of single crystal structural, thermodynamic, and reflectivity measurements of the double-perovskite Ba2NaOsO6. These characterize the material as a 5d1 ferromagnetic Mott insulator with an ordered moment of ∼0.2μB per formula unit and TC=6.8(3)  K. The magnetic entropy associated with this phase transition is close to Rln2, indicating that the quartet ground state anticipated from consideration of the crystal structure is split, consistent with a scenario in which the ferromagnetism is associated with orbital ordering.This article is from Physical Review Letters 99 (2007): 1, doi:10.1103/PhysRevLett.99.016404. Posted with permission.</p

Effect of screening of the electron-phonon interaction on mass renormalization and optical conductivity of the extended Holstein model polarons

An interacting electron-phonon system is considered within the Extended Holstein model at strong coupling regime and nonadiabatic approximation. It is assumed that screening of an electron-phonon interaction is due to the excess electrons in a lattice. An influence of the screening on the mass and optical conductivity of a lattice polarons is studied. A more general form Yukawa-type electron-phonon interaction potential potential is accepted and corresponding forces are derived in a lattice. It is emphasized that the screening effect is more pronounced at the values of screening radius comparable with a lattice constant. It is shown that the mass of a lattice polaron obtained using Yukawa-type electron-phonon interaction potential is less renormalized than those of the early studied works at the same screening regime. Optical conductivity of lattice polarons is calculated at different screening regimes. The screening lowers the value of energy that corresponds to the peak of the optical conductivity curve. The shift (lowering) is more pronounced at small values of screening radius too. The factors that give rise to this shift is briefly discussed.Comment: 8 pages, 10 figures, 1 table. arXiv admin note: substantial text overlap with arXiv:1308.219