08 Fakultät Mathematik und Physik

Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/9

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Institute: search.filters.UBSInstitut.Institut für Theoretische Physik IAuthor: search.filters.author.Rommel, Patric

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    Modell mit Mastergleichung zur Beschreibung der Exziton-Phonon-Wechselwirkung in Cu2O
    (2017) Rommel, Patric
    Exzitonen in äußeren Feldern sind ein wertvolles Modellsystem, um theoretische Vorhersagen über eine Vielzahl verschiedener Effekte experimentell zugänglich zu machen und zu überprüfen. Wichtig ist hier in erster Linie der Einfluss der Bandstruktur, durch welchen sich wichtige Korrekturen im Vergleich zum wasserstoffartigen Modell ergeben. Sie bildet unter anderem die reduzierte Symmetrie im Kristallgitter ab. Andererseits gibt es im Festkörper neben den Exzitonen auch andere Quasiteilchen deren Effekte zu beachten sind. In dieser Arbeit soll es dabei um die Exziton-Phonon-Wechselwirkung und ihren Einfluss auf das Eigenwertspektrum der Exzitonen gehen.
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    Theory of yellow and green excitons in cuprous oxide with emphasis on correction terms and external fields
    (2022) Rommel, Patric; Main, Jörg (Prof. Dr.)
    Cuprous oxide has played a central role in the history of exciton physics, being the semiconductor where excitons were first experimentally discovered. Excitons formed from an electron in its lowest conduction band and a hole from its the highest valence band belong to the yellow exciton series. Recently, optical absorption experiments have followed this series up to principal quantum number n = 25 [T. Kazimierczuk et al., Nature 514, 343 (2014)]. This opens up possibilities for novel applications using the particular attributes of highly excited Rydberg system, for example in quantum information processing. For this, the properties of the excitons have to be understood thoroughly. In this thesis, we aim to advance the theoretical knowledge of the yellow and green exciton series in cuprous oxide. We use numerical simulation and analytical methods to investigate in detail the exchange splitting of the S states, the fine structure splitting of the D excitons, spectra in external magnetic fields in Faraday and Voigt configuration, second harmonic generation in forbidden directions, and autoionizing spectra in external electric and parallel magnetic and electric fields. For the latter, we apply the complex-coordinate-rotation method, which we then further use to calculate the green exciton resonances lying in the yellow continuum. We present absorption spectra for transitions from the crystal ground state and for interseries transitions from the yellow to the green series.
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    Analysis of the fine structure of the D‐exciton shell in cuprous oxide
    (2021) Heckötter, Julian; Rommel, Patric; Main, Jörg; Aßmann, Marc; Bayer, Manfred
    The exciton states in cuprous oxide show a pronounced fine structure splitting associated with the crystal environment and the resulting electronic band structure. High‐resolution spectroscopy reveals an especially pronounced splitting of the yellow D excitons with one state pushed above any other state with the same principal quantum number. This large splitting offset is related to a strong mixing of these D states with the 1S exciton of the green series, as suggested by previously published calculations. Here, a detailed comparison of this theory with experimental data is given, which leads to a complete reassignment of the experimentally observed D exciton lines. The origin of different amounts of green admixture to D‐envelope states is deduced by analyzing the different terms of the Hamiltonian. The yellow-green mixing leads to level repulsion and induces an exchange interaction splitting to D‐envelope states, from which one of them becomes the highest state within each multiplet. Furthermore, the assignment of D exciton states according to their total angular momentum F is given and corrects an earlier description given in a former study.