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TT: Fachverband Tiefe Temperaturen

TT 2: Superconductivity: Sample Preparation, Characterization, Properties and Electronic Structure

TT 2.10: Vortrag

Montag, 16. März 2020, 12:00–12:15, HSZ 103

Evidence for an orbital dependent Mott transition in the ladders of (La, Ca)_xSr_14−xCu₂₄O₄₁ derived by electron energy-loss spectroscopy — •Friedrich Roth¹, Udo Ammerahl², Alexandre Revcolevschi², Bernd Büchner³, Martin Knupfer³, and Jörg Fink^3,4,5 — ¹Institute of Experimental Physics, TU Bergakademie Freiberg, Leipziger Straße 23, D-09599 Freiberg, Germany — ²Laboratoire de Physico-Chimie de l’État Solide, Université Paris-Sud, 91405 Orsay, France — ³IFW Dresden, P.O. Box 270116, D-01171 Dresden, Germany — ⁴Max Planck Institute for Chemical Physics of Solids, D-01187 Dresden, Germany — ⁵Institute for Solid-State and Material Physics, Technical University Dresden, D-01062 Dresden, Germany

The knowledge of the charge carrier distribution among the different orbitals of Cu and O is a precondition for the understanding of the physical properties of various Cu-O frameworks. We employ electron energy-loss spectroscopy to elucidate the charge carrier plasmon dispersion in (La, Ca)_xSr_14−xCu₂₄O₄₁ in dependency of x as well as temperature. We observe that the energy of the plasmon increases upon increasing Ca content, which signals an internal charge redistribution between the two Cu-O subsystems. Moreover, a comparison of the experimental plasmon excitations with RPA-like calculations indicates that the holes which are transferred to the Cu₂O₃ ladders are mainly located on O orbitals in the rungs and to a much lesser extent in those in the legs. This is related to a different filling of the bonding and antibonding band leading to an orbital dependent Mott transition.