The Electronic Band Structure of Strontium Titanate: Theory and Experiment

Abstract

The appropriate description of the 3d-valence electrons in transition metal oxides has been a subject of discussion for many years. Considering the heavy mass and low mobility of 3d-electrons (as compared to the values for these parameters in the “conventional” semiconductors), the question arises whether the band model is a legitimate representation of the energy states. Several features of the transition metal compounds have slowed down progress towards solution of this problem: magnetic ordering (NiO, CoO, MnO), complicated crystal structure (Fe₂O₃, Ti₂O₃), and low quality monocrystalline or polycrystalline samples. However, during the last few years considerable advances have been made. Better crystals have opened the door to more and better experiments. Although the nature of the transitions in many of these solids is extremely complex, some understanding of the mechanisms involved has been achieved (see the lecture by Dr. J. Feinleib). It has been established that the band model is more widely applicable than was previously assumed. In this area the theoretical and experimental work on SrTiO₃ (and related compounds) has been of major importance. The material has proven to be an ideal representative of the oxide family.

Major parts of the research discussed in this review have been supported by the U. S. National Aeronautics and Space Administration.