Fingerprints of the Jahn-Teller and superexchange physics in optical spectra of manganites

Abstract

Transition metal oxides incorporating Jahn-Teller (JT) ions Mn3+ (3d4) in manganites and Cu2+ (3d9) in cuprates exhibit outstanding magnetic and electronic properties, including colossal magnetoresistance (CMR) and high-temperature superconductivity (HTSC). The physics of these compounds is associated with the orbitally-degenerate electronic states of JT ions, leading to the linear electron-lattice interaction, complemented by the entirely electronic superexchange (SE) interaction. Here, we discuss the fingerprints of the JT and SE physics in the temperature-dependent complex dielectric function spectra and multi-order Raman scattering spectra measured in a detwinned LaMnO3 crystal, which is a famous compound exhibiting cooperative JT effect, being also a progenitor of magnetic materials exhibiting CMR effect. In accordance with the obtained experimental evidence, the associated effective parameters characterizing the JT and SE physics in manganites are presented.