  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.
