Correlations between Spectra and Resistivity in Transition Metal Oxides

Abstract

A comparison between photoconductivity spectra and resistivity in two transition metal oxides, La2–x Sr x CuO4 and La1–x Sr x VO3, is presented. The resistivities ρ­(T) for x < 0.05 in the cuprate and x < 0.28 in the vanadate are typical for single electron transfer. For T > 100 K, ρ­(T) – ρ(0) ∼ T 3/2. For higher dopings (x) the cuprate is a superconductor (x < 0.25) and the vanadate an ordinary metal. This tallies with the number of oxidation states and their spins when the electrons transfer locally. The insulator–metal transition and the vanishing of Cooper pairs are discussed in the conclusion.