Ab initio probing of the electronic band structure and Fermi surface of fluorine-doped WO3 as a novel low-T C superconductor

Abstract

First-principles calculations were performed to investigate the electronic structure and the Fermi surface of the newly discovered low-temperature superconductor: fluorine-doped WO 3 . We find that F doping provides the transition of the insulating tungsten trioxide into a metallic-like phase WO 3-x F x , where the near-Fermi states are formed mainly from W 5d with admixture of O 2p orbitals. The cooperative effect of fluorine additives in WO 3 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 WO 3 → WO 2.5 F 0.5 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. 74.20.Fg, 74.25.Jb,

Superconducting properties of theKxWO3tetragonal tungsten bronze and the superconducting phase diagram of the tungsten bronze family

“…of increased electronic concentration, on the insulating WO 3 system. The Fermi level (E F ) is shifted upward, 16,19 into the bottom of the conduction band. This leads to the metallic behavior of the K x WO 3 TTB-I phase up to the highest possible K doping level x = 0.6.…”

Electronic band structure and Fermi surface for new layered superconductor LaO0.5F0.5BiS2 in comparison with parent phase LaOBiS2 from first principles

“…Generally, it is quite an expected result, since for oxides, fluorine with one additional electron compared to oxygen may be considered as a "universal" electron dopant, which, owing to injection of additional electrons, changes the insulating oxides to metallic conductors or superconductors. For example, superconductivity was found at fluorine doping in simple insulating oxides such as WO 3 , see [25,26].…”

Mechanism of Reductive Fluorination by PTFE-Decomposition Fluorocarbon Gases for WO3

“…Among the transition-metal oxides investigated so far, reductive fluorination is particularly suited for WO 3 , a material of focus in both experimental and theoretical researches. ,,− WO 3 has been found to undergo complicated structural evolutions when subjected to certain conditions. For instance, when heat is applied, the low-temperature monoclinic (II) phase transforms into a monoclinic (I) phase via a triclinic structure.…”