Dresden 2026 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 46: Ultra-fast Phenomena II
HL 46.2: Talk
Thursday, March 12, 2026, 15:15–15:30, POT/0051
Coherent exciton-phonon coupling and many body interactions in halide perovskites probed by 2D electronic spectroscopy. — •Mohsin Sayar1, Katrin Winte1, Davide Caratti2, David Cahen2, Christoph Lienau1, and Antonietta De Sio1 — 1Carl von Ossietzky Universität, Oldenburg, Germany. — 2Weizmann Institute of Science, Rehovot, Israel
Exciton-phonon interactions are central to the unique optoelectronic properties of halide perovskites. Here we use temperature-dependent two-dimensional electronic spectroscopy (2DES) with 10 fs time resolution to study the exciton dynamics in bulk CH3NH3PbBr3 crystals. The 2DES maps distinguish between exciton and free-carrier-induced contributions to the near-band-edge optical nonlinearity, revealing distinct signatures of exciton-exciton and exciton-carrier many-body interactions. The ultrafast dynamics further reveal coherent low-frequency phonon oscillations at 40 cm−1 and 67 cm−1, corresponding to Pb-Br-Pb bending and stretching modes that most strongly couple to the exciton. Additionally, we observe faster, 105 fs exciton amplitude oscillations across all three crystal phases, arising from coherent population oscillations between 1s and 2p excitonic states, off-resonantly driven by the low-frequency coherent phonon fields in the crystal. We rationalize these results within a phenomenological model accounting for both exciton-phonon coupling and 1s-2p exciton coupling via the phonon fields. Preliminary polarization-resolved 2DES data show that these phonon-induced exciton oscillations are retained upon spin-selective excitation.
Keywords: Excitons; Hybrid Perovskites; Ultrafast Spectroscopy; Phonon Coupling