Optical spectroscopic studies of metal-insulator transitions in perovskite-related oxides

This article examines metal-insulator transitions observed in perovskite-li ke Ti-, V-, Mn-, Fe-, Co-, Ni-, Cu-, Bi-, and Ru-oxide systems using optica l spectroscopies, particularly infrared reflectance and Raman scattering. T he rich phenomena examined in these materials include bandfilling- and band width-induced metal-insulator transitions, mass renormalization effects, me tal-insulator transitions involving charge-, spin-, and orbital-ordering, c olossal magneto resistance, polaronic effects, double exchange ferromagneti sm, and electronic phase separation. In addition to describing the optical spectroscopic signatures of these remarkable phenomena, this article will e xamine theoretical models of this diverse behavior, and will explore some o f the outstanding questions confronting the physics of these materials.