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TT: Fachverband Tiefe Temperaturen

TT 80: Correlated Electrons: Poster

TT 80.40: Poster

Donnerstag, 21. März 2024, 15:00–18:00, Poster E

Optical investigation of altering correlation strength driven phase transition in 2D correlated molecular conductors — •Savita Priya, Dieter Schweitzer, and Martin Dressel — 1. Physikalisches Institut, Universität Stuttgart, Germany

Two-dimensional molecular electron systems are considered model systems for studying low-dimensional physics; exhibiting interesting phase diagrams with exotic charge and magnetic ordering phenomena, electronic correlations and coupling of the electron system with the underlying molecular and lattice system. The quasi-two-dimensional BEDT-TTF charge transfer salts can be tuned by chemical means, i.e. change of counter anion or partial atomic substitution in the organic layers, leading to a subtle modification of the coupling. Here we partialy substitute sulfur with selenium atoms in the organic framework of α-(BEDT-TTF)₂I₃, known for its metal-insulator phase transition at 135 K, forming α-(BEDT-STF)₂I₃ and α-(BEDT-TSF)₂I₃. We investigate changes in electronic behavior on the phase transition from the metallic to low temperature insulating phase in the substituted counterparts of α-(BEDT-TTF)₂I₃ (below 66 K for BEDT-STF and 40 K for BEDT-TSF). The chemical modification affects the molecular orbital overlap asymmetrically in BEDT-STF and symmetrically in BEDT-TSF. Our approach combines wide-ranged infrared spectroscopy with temperature variation (down to 12 K) to analyze changes in electronic response, focusing on order and temperature change of phase transition.

Keywords: Organic conductor; correlated electrons; phase transition; infrared spectroscopy