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arXiv · 2610.03274

Second-order Raman and anharmonic lattice dynamics in lead-halide perovskites

Chao Shen·Florian Kluibenschedl·Ayan A. Zhumekenov·Mikhail Lemeshko·Osman M. Bakr·Artem G. Volosniev·Zhanybek Alpichshev
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Abstract

We explore the microscopic origin of THz-driven lattice dynamics in methylammonium lead bromide CH$_3$NH$_3$PbBr$_3$ using two-dimensional THz Kerr-effect spectroscopy. The analysis of the experiment enables discrimination between competing nonlinear excitation mechanisms and reveals that the dominant pathway is phonon-mediated rather than purely photonic. In particular, we argue that the commonly observed 1.15~THz Raman-active $A_g$ mode is not excited directly by the THz electric field. Instead, it emerges through cubic anharmonic coupling to an infrared-active phonon at 0.68~THz. Furthermore, a satellite feature at 1.36~THz is identified as a two-phonon Raman response of the same infrared-active mode. The observation of strong quadratic coupling involving the infrared-active phonon suggests an unconventional form of electron-phonon dressing present in lead-halide perovskites.

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Chao Shen, Florian Kluibenschedl, Ayan A. Zhumekenov, Mikhail Lemeshko, Osman M. Bakr, Artem G. Volosniev, Zhanybek Alpichshev. 2026-10-02. Second-order Raman and anharmonic lattice dynamics in lead-halide perovskites. https://arxiv.org/abs/2610.03274

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