Origin of the mid-infrared peaks in the optical conductivity of LaMnO3

• Published in: Solid state communications 2021-08, Vol.334-335, p.114381, Article 114381
• Main Authors: Munkhbaatar, Purevdorj, Myung-Whun, Kim
• Format: Article
• Language: English
• Subjects: Infrared conductivity; LaMnO3; Phonon-coupled orbiton
• ISSN: 0038-1098; 1879-2766
• DOI: 10.1016/j.ssc.2021.114381

We calculated the infrared conductivity spectrum of orbitally ordered LaMnO3 in phonon frequency and overtone frequency ranges. We considered orbital exchange, Jahn-Teller electron–phonon coupling, and phonon–phonon coupling. The fundamental excitation of the phonon-coupled orbiton was only Raman active, not infrared active, while its overtone modes were both Raman and infrared active. Our calculations reproduced the small peaks near 1300 cm−1 observed both in Raman scattering and infrared conductivity spectra, as consistent with previous experimental results. •We show through calculation that the mid-infrared small peaks observed in LaMnO3 are the overtones of the Raman fundamental mode.•Raman fundamental mode is that the exchange interaction of the orbital pseudo-spin is strongly coupled with the Jahn-Teller phonon.•The Raman fundamental mode is a new form of basic excitation that appears due to the cooperative orbital ordering in LaMnO3.