Ab initio probing of the electronic band structure and Fermi surface of fluorine-doped WO3 as a novel low-TC superconductor
I. R. Shein, A. L. Ivanovskii
Institute of Solid State Chemistry, Ural Branch of the RAS, 620990 Ekaterinburg, Russia
Abstract
First-principles calculations were performed to investigate the
electronic structure and the
Fermi surface of the newly discovered low-temperature superconductor:
fluorine-doped WO3. We find that F doping provides the transition of the
insulating tungsten trioxide into a metallic-like phase WO3-xFx,
where the near-Fermi states are formed mainly from W 5d with admixture of O
2p-orbitals. The cooperative effect of fluorine additives in WO3
consists in change of electronic concentration as well as the lattice
constant. At probing their influence on the near-Fermi states separately, the
dominant role of the electronic factor for the transition of tungsten
oxyfluoride into superconducting state was established. The volume of the
Fermi surface gradually increases with the increase of the doping. In the
sequence WO3→ WO2.5F0.5 the effective atomic charges of W and O
ions decrease, but much less, than it is predicted within the idealized ionic
model - owing to presence of the covalent interactions W-O and W-F.