The metal-insulator transition in lanthanum strontium vanadate

Abstract

The electrical properties of La_1-xSr_xVO₃ change from those of a semiconductor to those of a metal as x is increased, with a metal-nonmetal transition occurring at x approximately=0.2. This has been studied using AC and DC conductivity and thermopower measurements over a temperature range from 4 to 400K. Evidence for localization is found in AC conductivity and a temperature dependent activation energy at temperatures below 100K. A temperature dependence sigma = sigma ₀exp(-B/T¹n/), where n approximately 4, is interpreted in terms of a model in which the Fermi level occurs within a tail of states at the edge of the valence band. No evidence is found for polaron formation, but the frequency dependence of AC conductivity suggests that multiple site hopping and possible cluster formation is of importance.