SKM 2021 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 1: Focus Session: When theory meets experiment: Hybrid halide perovskites for applications beyond solar

HL 1.5: Hauptvortrag

Montag, 27. September 2021, 12:15–12:45, H4

Unifying Ultrafast Polarization Responses of Lead Halide Perovskites via Two-Dimensional Optical Kerr Effect — •Sebastian F. Maehrlein — Columbia University, New York, USA — Fritz Haber Institute of the Max Planck Society, Berlin, Germany

The microscopic mechanism behind the outstanding optoelectronic properties of lead halide perovskites (LHPs) may lead to novel design principles for defect tolerant semiconductors, but is still highly debated. Previous studies, investigating the LHPs' ultrafast polarization response by the optical Kerr effect lead to dynamic screening models, which suggest charge carrier protection by large polarons and/or liquid-like screening.

Here, we finally decode the variety of nonlinear polarization signals by developing two-dimensional optical Kerr effect (2D-OKE) spectroscopy. We unveil a surprisingly unified origin: Both (inorganic and hybrid) LHP responses are governed by nonlinear mixing of anisotropic and highly dispersive light propagation near the optical band gap [1]. Based on the 2D-OKE fingerprint, we quantify dispersion anisotropy, follow phase transitions and trace lattice parameters of hybrid alloyed LHPs; supported by a comprehensive four-wave-mixing model. Moreover, our findings raise the awareness in all types of polarization sensitive pump-probe experiments and their modeling, where oscillatory signals are commonly assigned to coherent low-energy excitations (e.g. phonons, magnons, etc.). The presented works were mainly performed with L. Huber, F. Wang, and P.P. Joshi at X.-Y. Zhu group (Columbia U). [1] S. F. Maehrlein et al., DOI:10.1073/pnas.2022268118