Browsing by Author "Winkler, Mario"

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Open Access
The electronic and geometric structure of chemically immobilised catalysts in mesopores
(2023) Winkler, Mario; van Slageren, Joris (Prof. Dr.)
Open Access
Facile synthesis and characterization of pure tochilinite‐like materials from nanoparticulate FeS
(2022) Bolney, Robert; Grosch, Mario; Winkler, Mario; Slageren, Joris van; Weigand, Wolfgang; Robl, Christian
In this work, three different tochilinite‐like materials have been obtained by sophisticated synthetic methods that allow to control the distribution of iron ions. The purity of the samples was confirmed by powder X‐ray diffraction. From elemental analysis and Mössbauer spectroscopy data, detailed compositions could be determined: T1) Fe0.76S*0.86 [Fe2+0.01Fe3+0.56Mg2+0.43(OH)2.01]; T2) Fe0.89S*0.85 [Fe2+0.55Fe3+0.11Al3+0.33(OH)1.84(O)0.16]; T3) Fe0.71S*0.79 [Fe2+0.25Fe3+0.73Mg2+0.01Al3+0.01(OH)1.98(O)0.02]. These compositions fit to typical compositions of tochilinite in regard of the amount of iron vacancies and the volume ratio of the hydroxide layers to the sulfide layers. Besides hydroxide ions, oxide ions are also present in the hydroxide layers as a result of surface oxidation after the synthesis due to the high reactivity of the particles. TEM and SEM investigations show that the obtained powders consist mainly of thin sheets accompanied by nanotubes with BET surface areas ranging between 20 m2/g and 40 m2/g. The thermal stability was investigated by TGA and DSC analysis and it depends significantly on the composition.
Open Access
Hybrid spintronic materials from conducting polymers with molecular quantum bits
(2020) Kern, Michal; Tesi, Lorenzo; Neusser, David; Rußegger, Nadine; Winkler, Mario; Allgaier, Alexander; Gross, Yannic M.; Bechler, Stefan; Funk, Hannes S.; Chang, Li‐Te; Schulze, Jörg; Ludwigs, Sabine; Slageren, Joris van
Hybrid materials consisting of organic semiconductors and molecular quantum bits promise to provide a novel platform for quantum spintronic applications. However, investigations of such materials, elucidating both the electrical and quantum dynamical properties of the same material have never been reported. Here the preparation of hybrid materials consisting of conducting polymers and molecular quantum bits is reported. Organic field‐effect transistor measurements demonstrate that the favorable electrical properties are preserved in the presence of the qubits. Chemical doping introduces charge carriers into the material, and variable‐temperature charge transport measurements reveal the existence of mobile charge carriers at temperatures as low as 15 K. Importantly, quantum coherence of the qubit is shown to be preserved up to temperatures of at least 30 K, that is, in the presence of mobile charge carriers. These results pave the way for employing such hybrid materials in novel molecular quantum spintronic architectures.
Open Access
Modular approach to creating functionalized surface arrays of molecular qubits
(2023) Tesi, Lorenzo; Stemmler, Friedrich; Winkler, Mario; Liu, Sherri S. Y.; Das, Saunak; Sun, Xiuming; Zharnikov, Michael; Ludwigs, Sabine; Slageren, Joris van
The quest for developing quantum technologies is driven by the promise of exponentially faster computations, ultrahigh performance sensing, and achieving thorough understanding of many‐particle quantum systems. Molecular spins are excellent qubit candidates because they feature long coherence times, are widely tunable through chemical synthesis, and can be interfaced with other quantum platforms such as superconducting qubits. A present challenge for molecular spin qubits is their integration in quantum devices, which requires arranging them in thin films or monolayers on surfaces. However, clear proof of the survival of quantum properties of molecular qubits on surfaces has not been reported so far. Furthermore, little is known about the change in spin dynamics of molecular qubits going from the bulk to monolayers. Here, a versatile bottom‐up method is reported to arrange molecular qubits as functional groups of self‐assembled monolayers (SAMs) on surfaces, combining molecular self‐organization and click chemistry. Coherence times of up to 13 µs demonstrate that qubit properties are maintained or even enhanced in the monolayer.