Metal-nonmetal transition in amorphous mixtures of Cs and Au

Electrical transport and optical measurements are reported on amorphous mixtures of Cs and Au at 6 K. The two metal-nonmetal transitions exhibited on either side of the stoichiometric compound CsAu are studied as a function of composition. The role of the ionic bond in the transition is discussed in relation to the character of the composition dependence of the physical properties investigated. Both the electrical transport and the optical data indicate that the transitions occur at the Cs atomic fractions 0.25 ± 0.02 and 0.60 ± 0.01 and that at compositions between these the states are localized at the Fermi energy. Comparisons are made with data on liquid Cs-Au mixtures.