Orbital-order phase transition and non-adiabatic quantum-classical dynamics in strongly coupled electron-phonon systems

ten Brink, Michael Wilhelm

dc.contributor.advisor	Blöchl, Peter E. Prof. Dr.
dc.contributor.author	ten Brink, Michael Wilhelm
dc.date.accessioned	2023-06-01T13:09:55Z
dc.date.available	2023-06-08T00:50:12Z
dc.date.issued	2023-06-01
dc.identifier.uri	http://resolver.sub.uni-goettingen.de/purl?ediss-11858/14697
dc.identifier.uri	http://dx.doi.org/10.53846/goediss-9912
dc.format.extent	213	de
dc.language.iso	eng	de
dc.rights.uri	http://creativecommons.org/licenses/by/4.0/
dc.subject.ddc	530	de
dc.title	Orbital-order phase transition and non-adiabatic quantum-classical dynamics in strongly coupled electron-phonon systems	de
dc.type	doctoralThesis	de
dc.contributor.referee	Blöchl, Peter E. Prof. Dr.
dc.date.examination	2022-11-25	de
dc.subject.gok	Physik (PPN621336750)	de
dc.description.abstracteng	This thesis contributes to the investigation of solid-state systems with a strong coupling between electrons and the surrounding atomic lattice (phonons). One focus point of the thesis is the material class of $Pr_{1-x}Ca_{x}MnO_3$ (PCMO), a strongly correlated perovskite manganese oxide, which shows a photovoltaic effect that is highly influenced by the electron-phonon interactions present in the material. We use a theoretical model including electron, phonon, and spin degrees of freedom in a combined quantum-mechanical/classical description to investigate ground-state ordered phases and the breakdown of long-range orbital order in low-doped PCMO with increasing temperature. Our results support new experimental evidence that the spontaneous orbital-order phase transition takes place at much lower temperatures than previously believed and correlates with the onset of the photovoltaic effect. In the second part of the thesis, we analyze in more detail the ability of quantum-classical methods to describe non-adiabatic electron-phonon dynamics, which is needed for an adequate description of excited charge carriers in polaronic materials, e.g., after a photoexcitation. We present a detailed benchmark study of two such methods, multitrajectory Ehrenfest (MTE) and fewest-switches surface hopping (FSSH), in a prototypical system with electron-phonon coupling: the Holstein model. We discuss the strengths and weaknesses of both methods, with a special focus on the importance of various initial states. In most studied cases, the FSSH method yields a better description of both the mobility/spreading of the excited charge carrier and the electron-nuclear energy transfer, making it a suitable method for further analysis of the PCMO photovoltaic effect in future studies.	de
dc.contributor.coReferee	Heidrich-Meisner, Fabian Prof. Dr.
dc.subject.eng	Theoretical physics	de
dc.subject.eng	Solid-state physics	de
dc.subject.eng	Polaronic materials	de
dc.subject.eng	Perovskites	de
dc.subject.eng	Manganites	de
dc.subject.eng	Photovoltaics	de
dc.subject.eng	Holstein model	de
dc.subject.eng	Multitrajectory Ehrenfest	de
dc.subject.eng	Fewest-switches surface hopping	de
dc.identifier.urn	urn:nbn:de:gbv:7-ediss-14697-2
dc.affiliation.institute	Fakultät für Physik	de
dc.description.embargoed	2023-06-08	de
dc.identifier.ppn	1847360874
dc.notes.confirmationsent	Confirmation sent 2023-06-01T13:15:01	de

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