Anderson localization in tungsten bronzes A numerical study

Abstract

We report numericai results for electron localization induced by disorder in the tungsten bronzes Na_xWO₃, Na_xTa_yW_1−y O₃ and Na_xWO_3-y F_y The bronzes are described by a nearest-neighbour tight-binding Hamiltonian. Anderson-type disorder is introduced into the transition-metal atoms. The localization properties of eigenfunctions are deduced from the scaling behaviour of the correlation length. The calculated density of states is used to compare the numerical results with photoelectron spectra. A metal-non-metal transition is indicated at a critical concentration of electrons in the conduction band of x_c ≈ 0.3, which is independent of the degree of F or Ta substitution.