  Strontium titanate (SrTiO3, STO) is a critically important material for the
study of emergent electronic phases in complex oxides, as well as for the
development of applications based on their heterostructures. Despite the large
body of knowledge on STO, there are still many uncertainties regarding the role
of defects in the properties of STO, including their influence on
ferroelectricity in bulk STO and ferromagnetism in STO-based heterostructures.
We present a detailed analysis of the decay of persistent photoconductivity in
STO single crystals with defect concentrations that are relatively low but
significantly affect their electronic properties. The results show that
photo-activated electron transport cannot be described by a superposition of
the properties due to independent point defects as current models suggest but
is, instead, governed by defect complexes that interact through dynamic
correlations. These results emphasize the importance of defect correlations for
activated electronic transport properties of semiconducting and insulating
perovskite oxides.
