Simplicity out of complexity: band structure for W$_{20}$O$_{58}$ superconductor

TL;DR

This study uses density functional theory to analyze the band structure of the complex superconductor W20O58, revealing a simplified low-energy electronic structure dominated by tungsten d-orbitals despite structural complexity.

Contribution

It demonstrates that the complicated structure of W20O58 results in a manageable low-energy band structure, highlighting the role of tungsten d-orbitals in its superconductivity.

Findings

Low-energy bands are limited to no more than 10 per spin projection.

Fermi level crosses approximately 9-10 bands from tungsten d-orbitals.

The complex structure simplifies to a feasible electronic model.

Abstract

The band structure, density of states, and the Fermi surface of a recently discovered superconductor, oxygen-deficient tungsten oxide WO$_{2.9}$ that is equivalent to W$_{20}$O$_{58}$, studied within the density functional theory (DFT) in the generalized gradient approximation (GGA). Here we show that despite the extremely complicated structure containing 78 atoms in the unit cell, the low-energy band structure is quite feasible. Fermi level is crossed by no more than 10 bands per one spin projection (and even 9 bands per pseudospin projection when the spin-orbit coupling is considered) originating from the $d$-orbitals of tungsten atoms forming zigzag chains.