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.