Superconductivity in the tungsten bronze Rb{sub x}WO{sub 3} (0.20{<=}x{<=}0.33) in connection with its structure, electronic density of states, and phonon density of states
- Institut NEEL, CNRS and UJF, Boite Postale 166, 38042 Grenoble Cedex 9 (France)
We have measured the magnetic susceptibility of the Rb{sub x}WO{sub 3} compound (0.20{<=}x{<=}0.33) and examined its structural properties and lattice dynamics, using elastic and inelastic neutron scattering (INS) experiments, in order to gain further insight into the unusual features of its superconducting state, namely (i) the stabilizing effect resulting from the reduction of rubidium content, i.e., of the conduction electron density [what we shall name the ''T{sub c} (x) paradox''], and (ii) the destabilizing effect of the ordering of the Rb ions. We also performed density-functional calculations of the phonon dispersion in the ''stoichiometric'' Rb{sub 0.33}WO{sub 3} and Cs{sub 0.33}WO{sub 3} to identify the main features of the phonon spectra. These calculations give a very satisfactory description of the INS data and confirm the assignment to these bronzes of a lower (orthorhombic) symmetry than previously proposed. Our results contradict the previous interpretations of the T{sub c} (x) paradox and of the ordering effect: (i) no general softening of the lattice accompanies the increase of the Rb-vacancy population and (ii) no general decrease of the electron density of states D{sub EF} distinguishes the ordered nonsuperconducting Rb{sub 0.25}WO{sub 3} from its neighboring disordered parents. It appears, therefore, that the electron-electron coupling in this system probably proceeds through well-defined electronic states and phonons. This is a feature these ''hexagonal'' tungsten bronzes (HTB) apparently share with several high-T{sub c} materials. We discuss what could be the mechanisms responsible for the very selective electron-phonon coupling in the HTB.
- OSTI ID:
- 21052754
- Journal Information:
- Physical Review. B, Condensed Matter and Materials Physics, Vol. 76, Issue 17; Other Information: DOI: 10.1103/PhysRevB.76.174511; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BRONZE
CESIUM COMPOUNDS
DENSITY FUNCTIONAL METHOD
ELECTRON DENSITY
ELECTRON-ELECTRON COUPLING
ELECTRON-PHONON COUPLING
INELASTIC SCATTERING
MAGNETIC SUSCEPTIBILITY
NEUTRON DIFFRACTION
NEUTRON REACTIONS
ORTHORHOMBIC LATTICES
PHONONS
RUBIDIUM
RUBIDIUM COMPOUNDS
RUBIDIUM IONS
SUPERCONDUCTIVITY
TUNGSTEN BRONZE
TYPE-II SUPERCONDUCTORS
VACANCIES