Self-trapped Exciton and Franck-Condon Spectra Predicted in LaMnO$_3$

TL;DR

This paper predicts that in LaMnO$_3$, electronic excitations self-trap due to Jahn-Teller effects, leading to characteristic Franck-Condon vibrational spectra and multiphonon features in Raman spectra, offering a new interpretation of existing data.

Contribution

It introduces a theoretical prediction of self-trapped excitons and Franck-Condon spectra in LaMnO$_3$, providing a novel interpretation of experimental spectra.

Findings

Optical spectrum shows Gaussian Franck-Condon vibrational sidebands.

Raman spectrum predicted to have strong multiphonon features.

Existing data reinterpreted in terms of self-trapped excitons.

Abstract

Because the ground state has cooperative Jahn-Teller order, electronic excitations in LaMnO$_3$ are predicted to self-trap by local rearrangement of the lattice. The optical spectrum should show a Franck-Condon series, that is, a Gaussian envelope of vibrational sidebands. Existing data are reinterpreted in this way. The Raman spectrum is predicted to have strong multiphonon features.