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HL: Fachverband Halbleiterphysik

HL 26: Poster II

HL 26.27: Poster

Mittwoch, 11. März 2026, 09:30–11:30, P1

Excitonic Reststrahlen Effect in (PEA)₂PbI₄ — •Michael Pfeufer, Patrick Grenzer, Friedrich Schöppler, and Tobias Hertel — Institute of Physical and Theoretical Chemistry, Julius-Maximilains-University Würzburg, Germany

Layered Ruddlesden-Popper perovskites with their natural quantum well structure allow for strongly confined excitons with very high oscillator strengths. In this work, evidence of an excitonic Reststrahlen effect, a phenomenon in which strong exciton resonances push the real permittivity below zero, was identified and characterized in phenethylammonium lead iodide (PEA)₂PbI₄. Transfer-matrix method simulations of the thin film were employed to fit temperature-dependent transmission measurements to an isotropic Lorentz oscillator model and to extract the dielectric function of the material. Additionally, we show that the behaviour of the Reststrahlen band in thickness-dependent transmission spectra is consistent with that found in other materials featuring a Reststrahlen-like response. Electric field calculations inside the material slab suggest natural exciton-polaritonic formation in the material, as well as longitudinal modes near the zero crossing of the real permittivity.