Browsing Fakultät für Physik (inkl. GAUSS) by Referee "Kehrein, Stefan Prof. Dr."
Now showing items 1-18 of 18
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Eigenstate overlaps in the Transverse Field Ising Model and the Axial Next Nearest Neighbour Model
(2024-05-03)In this thesis, a possible extension of the adiabatic theorem for quantum quenches, i.e. non-adiabatic changes, is checked for its validity. In particular, the Transverse Field Ising Model (TFIM) and the related Axial Next ... -
Non-Equilibrium Dynamics of Photoexcited Correlated Quantum Matter
(2024-01-22)The interaction of time-dependent electromagnetic fields with electrons in quantum materials can give rise to many both fundamentally interesting as well as technologically relevant phenomena like transient band structure ... -
Tripartite Information and Scrambling in Quantum Many-Body Systems
(2023-05-11)This thesis contributes to the study of quantum chaos and thermalization of closed quantum systems by applying tools from quantum information theory. We study scrambling – the delocalization of quantum information – in ... -
Microscopic foundation of the Eigenstate Thermalization Hypothesis
(2023-03-20)The Eigenstate Thermalization Hypothesis (ETH) explains how isolated quantum many-body systems thermalize by proposing that each energy eigenstate is already thermal. The hypothesis is believed to be essential to the ... -
Transport and dynamical properties of electron-phonon coupled systems
(2023-01-31)In this thesis, I investigate the transport and dynamical properties of electron-phonon coupled systems using numerical methods. I focus on the one-dimensional Holstein model, which incorporates both polaron and charge ... -
Matrix Product State Approaches to Non-equilibrium Spectral Quantities of Strongly Correlated Fermions in One Dimension
(2022-06-09)In this thesis we numerically study non-equilibrium phenomena in one-dimensional quantum many-body systems. We discuss extensions of the concepts of spectral functions and of the optical conductivity to time-dependent ... -
Density Functional Theory Simulations of Rare-Earth Hexaborides: Bulk and Surface Studies
(2021-12-13)Rare-earth hexaborides are boron-rich solid state compounds and belong to the strongly correlated electron materials. The physics of the rare-earth hexaborides is strongly influenced by the filling of the 4f atomic shells ... -
Quantum quench dynamics in the transverse field Ising model of fully connected spins
(2021-04-06)The transverse field Ising model of N fully connected spins provides a mathematical accessible, yet non-trivial, system to investigate the non-thermal dynamics after a sudden quantum quench. The focus in this thesis is ... -
Topological and non-equilibrium superconductivity in low-dimensional strongly correlated quantum systems
(2020-05-11)Superconductivity in its various manifestations has been stimulating both experimental and theoretical progress in condensed-matter physics for more than a hundred years. The remarkable property of electrons to pair up ... -
A Unitary Perturbation Theory Approach to Real-Time Evolution in the Hubbard Model
(2019-10-29)We advance perturbative approaches for out-of-equilibrium quantum many-body systems by applying unitary perturbation theory to the real-time evolution of the weakly interacting Hubbard model in d > 1 dimensions. We derive ... -
Ballistic electron transport in graphene nanodevices and billiards
(2019-10-17)Nanodevices are objects with broad relevance for today's society, which bases its economy, operation, and communication onto digital resources. In ballistic nanodevices, disorder has either negligible or minor impact on ... -
Photoexcitations of Model Manganite Systems using Matrix-Product States
(2019-01-30)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 ... -
Dynamics of isolated quantum many-body systems far from equilibrium
(2018-01-22)This thesis addresses different aspects of the dynamics of isolated quantum many-body systems far from equilibrium, ranging from transient phenomena at short times to questions about relaxation and equilibration at late ... -
A Variational Cluster Approximation for the Heisenberg Model
(2017-04-13)In this thesis we present a novel variational cluster approximation for Heisenberg spin systems. It is based on the self-energy functional theory by Potthoff for fermionic and bosonic models with local interactions. To ... -
Thermalization in one-dimensional quantum-many-body systems
(2017-01-16)We consider the thermalization of the momentum distribution in two one-dimensional models. The first one is the integrable Hubbard model with an additional integrability breaking term in the Hamiltonian, which is a ... -
Unbiased evaluation and development of Green's-function-based density-matrix functionals
(2016-10-25)Ab-initio calculations are dominated by density functional theory (DFT), which provides an efficient and accurate description of the electronic structure for most materials. For materials with strong correlations, however, ... -
Braided Actions of DHR Categories and Reconstruction of Chiral Conformal Field Theories
(2016-10-18)Quantum Field Theory (QFT) is our modern understanding of particles and matter at small scales, where quantum behaviour replaces macroscopical phenomena, which are much closer to intuition, and dynamics is rather driven ... -
Finite-temperature dynamics of low-dimensional quantum systems with DMRG methods
(2016-08-17)This thesis is concerned with the numerical study of one-dimensional (1D) spin-1/2 quantum magnets and related method development. Its focus is on the calculation of dynamical spin correlation functions both at zero and ...