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arXiv · 1407.1409

Anomalous multi-order Raman scattering in LaMnO_3: a signature of a quantum lattice effect in a Jahn-Teller crystal

N. N. Kovaleva·O. E. Kusmartseva·K. I. Kugel·A. A. Maksimov·D. Nuzhnyy·A. M. Balbashov·E. I. Demikhov·A. Dejneka·V. A. Trepakov·F. V. Kusmartsev·A. M. Stoneham
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Abstract

The multi-order Raman scattering is studied up to a fourth order for a detwinned LaMnO_3 crystal. Based on a comprehensive data analysis of the polarisation-dependent Raman spectra, we show that the anomalous features in the multi-order scattering could be the sidebands on the low-energy mode at about 25 cm-1. We suggest that this low-energy mode stems from the tunneling transition between the potential energy minima arising near the Jahn-Teller Mn3+ ion due to the lattice anharmonicity, and the multi-order scattering is activated by this low-energy electronic motion. The sidebands are dominated by the oxygen contribution to the phonon density-of-states, however, there is an admixture of an additional component, which may arise from coupling between the low-energy electronic motion and the vibrational modes.

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N. N. Kovaleva, O. E. Kusmartseva, K. I. Kugel, A. A. Maksimov, D. Nuzhnyy, A. M. Balbashov, E. I. Demikhov, A. Dejneka, V. A. Trepakov, F. V. Kusmartsev, A. M. Stoneham. 2014-07-05. Anomalous multi-order Raman scattering in LaMnO_3: a signature of a quantum lattice effect in a Jahn-Teller crystal. https://doi.org/10.1088/0953-8984%2F25%2F15%2F155602

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