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

TL;DR

This study uses first-principles calculations to explore how fluorine doping transforms WO3 into a low-temperature superconductor by altering its electronic structure and Fermi surface, highlighting the dominant electronic effects over lattice changes.

Contribution

It provides a detailed ab initio analysis of the electronic and Fermi surface evolution in fluorine-doped WO3, revealing the key role of electronic factors in inducing superconductivity.

Findings

F doping turns WO3 into a metallic-like phase

Fermi surface volume increases with doping

Electronic effects dominate over lattice changes in superconductivity transition

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 \rightarrow 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.