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DS: Fachverband Dünne Schichten

DS 20: Poster

DS 20.30: Poster

Donnerstag, 12. März 2026, 18:30–20:30, P2

From Localised to Delocalised Charge Carriers: An Optical Investigation on Metal-Insulator Transitions — •Thomas Schmidt¹, Navjot Bamrah², Liron B. Michael², Ricardo P. M. S. Lobo³, and Matthias Wuttig^1,2 — ¹Peter Grünberg Institute - JARA-Institute Energy Efficient Information Technology (PGI-10), Jülich, Germany — ²I. Institute of Physics (IA), RWTH Aachen University, Germany — ³LPEM, ESPCI Paris, CNRS, PSL University, 75231 Paris, France

Understanding metal-insulator transitions (MITs) has been a central topic in solid-state physics and materials science for decades. Various theoretical frameworks describe these transitions in terms of critical charge carrier densities (Mott MIT) or electron localisation induced by disorder (Anderson MIT). Typically, electrical conductivity measurements or their temperature-dependent derivative (TCR) are used to distinguish metallic from insulating behavior.

In this work, we propose an alternative approach based on optical spectroscopy. Reflectance spectra were recorded over a broad spectral range using a Fourier-transform infrared (FTIR) spectrometer. The optical functions were subsequently obtained through modeling of the measured data. Our analysis focuses on the evolution of the Drude response in the optical conductivity, which directly reflects the dynamics of free charge carriers. The Drude feature, defined by the ratio of the plasma edge to the scattering rate, provides valuable insight into the material-specific degree of electron (de)localisation and thus offers an alternative perspective on MITs and their relation to chemical bonding.

Keywords: Optics; FTIR; Drude Model; Metavalent Bonding; Metal-Insulator Transition