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dc.contributor.advisor Manmana, Salvatore R. PD Dr.
dc.contributor.author Köhler, Thomas
dc.date.accessioned 2019-01-30T11:48:05Z
dc.date.available 2019-01-30T11:48:05Z
dc.date.issued 2019-01-30
dc.identifier.uri http://hdl.handle.net/11858/00-1735-0000-002E-E579-B
dc.language.iso eng de
dc.rights.uri http://creativecommons.org/licenses/by-nc-nd/4.0/
dc.subject.ddc 530 de
dc.title Photoexcitations of Model Manganite Systems using Matrix-Product States de
dc.type doctoralThesis de
dc.contributor.referee Manmana, Salvatore R. PD Dr.
dc.date.examination 2019-01-18
dc.subject.gok Physik (PPN621336750) de
dc.description.abstracteng The emergence of order in materials with strongly-correlated electrons in out-of-equilibrium situations inspires a lot of new research, both experimental and theoretical. The main goal of this theoretical research project is to better understand related questions in the dynamics in a strongly correlated many-body state after a photoexcitation has occured. Such situations are usually not fully explainable in a mean-field picture nor analytically solvable. Hence, advanced numerical techniques are necessary. In this work, we investigate non-equilib- rium situations after photoexcitations. In order to model a hypothetical one-dimensional (1D) manganite, we chose the 1D Hubbard model with nearest-neighbor interaction and a staggered magnetic field. The photoexcitation is modeled in two different ways: First we investigate sud- den, local excitations, and afterwards we study a semi-classical approach by applying the Peierls substitution, which leads to a time-dependent Hamiltonian. All simulations are performed with an implementation of the time-dependent density-matrix renormalization group (DMRG), which is formulated by tensor-network states (TNSs), namely matrix-product states (MPSs) and matrix-product operators (MPOs). The framework used offers the possibility that every MPO can be externally described by finite-state machines (FSMs), hence it is extremely flexible. In this thesis, we explain how to perform exact FSM arithmetics, and how to compress the resulting FSMs. Based on MPSs and FSMs, a quantum-computer simulator (QCS) is introduced, which is mainly used as a universal tool for (MPS)-quantum- state manipulations. From the investigations with the sudden, local excitations, we learned that the electron-electron interaction is responsible for a rapid relaxation of the magnetic moment of the individual bands. Nevertheless, this relaxation can be stalled via a stronger magnetic microstructure. By applying a spin-selective photoexcitation via the Peierls substitution, we are able to induce a meta-stable charge-density wave (CDW) pattern if a magnetic microstructure is present. For a small, but finite interaction, we find a decay channel for the doublon-based part of the CDW, which still leaves a finite pattern. For large interaction, nearly no doublons are created by the photoexcitation. In the opposite limit, i.e., the non-interacting case, the two spin species are decoupled. Hence, in both limits the decay channel does not weaken the CDW and we find the pattern to be stable up to the times we can treat. de
dc.contributor.coReferee Kehrein, Stefan Prof. Dr.
dc.contributor.thirdReferee Honecker, Andreas Prof. Dr.
dc.subject.eng Matrix-Product States de
dc.subject.eng charge-density wave de
dc.subject.eng quantum-computer simulator de
dc.subject.eng photoexcitation de
dc.identifier.urn urn:nbn:de:gbv:7-11858/00-1735-0000-002E-E579-B-1
dc.affiliation.institute Fakultät für Physik de
dc.identifier.ppn 1047737833

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