SKM 2023 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 33: Perovskite and photovoltaics II (joint session HL/CPP)
CPP 33.8: Talk
Wednesday, March 29, 2023, 12:00–12:15, JAN 0027
Phonon-driven Intra-exciton Rabi Oscillations in Halide Perovskites — •Katrin Winte1, Xuan Trung Nguyen1, Daniel Timmer1, Davide Ceratti2, Caterina Cocchi1, Michael Lorke3, Frank Jahnke3, David Cahen2, Christoph Lienau1, and Antonietta De Sio1 — 1University of Oldenburg, Germany — 2Weizmann Institute of Science, Israel — 3University of Bremen, Germany
There is increasing consensus that in halide perovskites (HaPs) the interaction of electronic excitations with the phonon modes of their flexible polar lattice is crucial for the unique optoelectronic and transport properties of these materials. Here we show that coherent low frequency phonon of the lead-halide lattice induce Rabi oscillations between 1s and 2p excitons in CsPbBr3 crystals. Ultrafast two-dimensional electronic spectroscopy reveals an excitonic peak structure oscillating with a 100-fs period up to 2 ps at 20 K. This frequency does not match any phonon modes of the crystals. Only after 2 ps, slow coherent phonon oscillations dominate the dynamics. We rationalize these findings as off-resonant intra-exciton Rabi oscillations induced by the Pb-Br phonon fields of the HaP crystals. We show that the slow motion of Pb-Br sublattice induces electric fields at THz frequencies that are sufficiently strong to drive off-resonant population oscillations between 1s and 2s excitons. Model simulation of the nonlinear optical response support this interpretation. This goes beyond prevailing models for the electron-phonon coupling in HaPs. It suggests that the coupling of characteristic low frequency phonon to intra-excitonic transitions may be the key to control their anharmonic response.