Manifestation of vibronic dynamics in infrared spectra of Mott insulating fullerides

In order to probe the nature of Jahn-Teller dynamics in alkali-doped fullerides, the fine structure and temperature evolution of infrared spectra have been intensively used last years [1,2]. At the same time, theoretical framework to adequately extract the information on the complicated vibronic dynamics from infrared spectra is still lacking. In this work, the first-principles theory of the infrared spectra of dynamical Jahn-Teller system is developed and applied to the Mott-insulating Cs₃C₆₀ [3]. With the calculated coupling parameters for Jahn-Teller and infrared active vibrational modes, the manifestation of the dynamical Jahn-Teller effect in infrared spectra is elucidated. In particular, the temperature evolution of the infrared line shape is explained. The transformation of the latter into Fano resonance type in metallic fulleride [2] is discussed on the basis of obtained results.

[1] G. Klupp et al., Nat. Commun. 3, 912 (2012).
[2] R. H. Zadik et al., Sci. Adv. 1, e1500059 (2015).
[3] Y. Matsuda, N. Iwahara, K. Tanigaki, and L. F. Chibotaru, Phys. Rev. B 98, 165410 (2018).