Two-Dimensional Character of the Conduction Bands ofd-Band Perovskites

Abstract

The lowest conduction bands of a number of perovskites are determined principally by the ($\mathrm{pd}\pi$) interaction which mixes the $t_{2g} d$ orbitals of the transition-metal ion with the $p$ orbitals of the oxygen. Because of the planar character of the ($\mathrm{pd}\pi$) interaction, each of the three equivalent $t_{2g}$ conduction bands depends strongly on only two of the components of the wave vector. As a result, the bands possess a two-dimensional character which accounts for the characteristic structure in the density of states and the optical properties of SrTi${\mathrm{O}}_3$, BaTi${\mathrm{O}}_3$, and KTa${\mathrm{O}}_3$.