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@PHDTHESIS{Ortmanns:960727,
      author       = {Ortmanns, Lara Celine},
      othercontributors = {Wegewijs, Maarten Rolf and Splettstößer, Janine and
                          Meden, Volker},
      title        = {{F}rom 2d-van der {W}aals magnets to superconductor hybrid
                      devices},
      volume       = {5348},
      school       = {RWTH Aachen University},
      type         = {Dissertation},
      address      = {Aachen},
      publisher    = {RWTH Aachen University},
      reportid     = {RWTH-2023-06360},
      isbn         = {978-91-7905-882-1},
      series       = {Doktorsavhandlingar vid Chalmers tekniska högskola},
      pages        = {1 Online-Ressource : Illustrationen, Diagramme},
      year         = {2023},
      note         = {Druckausgabe: 2023. - Auch veröffentlicht auf dem
                      Publikationsserver der RWTH Aachen University. -
                      Cotutelle-Dissertation; Dissertation, RWTH Aachen
                      University, 2023. - Dissertation, Chalmers University of
                      Technology Göteburg, 2023},
      abstract     = {In this thesis, we focus on two distinct topics in
                      different lines of research within mesoscopic physics, the
                      first is related to spin-waves in 2d-van der Waals magnets,
                      the second to the transient dynamics of a quantum dot device
                      attached to a normal metal and proximized with a
                      superconducting material. Based on our earlier work on the
                      magnon dispersion in bilayers of 2d-ferromagnets, in this
                      thesis we complement the earlier work by further analyzing
                      the competing interactions in the Hamiltonian. Moreover, we
                      explain the magnon dispersion degeneracy and the topology of
                      the magnon spectrum in terms of an underlying PT-symmetry.
                      As a result, we can exclude a magnon (thermal) Hall effect
                      for our type of exchange anisotropy spin model, but indicate
                      extensions of our model that would allow for non-trivial
                      topological effects. The analysis of this first topic
                      amounts to a study of equilibrium properties of 2d bulk
                      materials, which exhibit magnetic order. The relevant
                      excitations of interest are magnons, which are bosons.
                      Differently, for the second topic we deal with the transient
                      dynamics of a quantum dot device after a switch in gate
                      voltage, where instead of magnetic order we have
                      superconducting order in the lead attached, which induces a
                      pronounced proximity effect on the sensitive quantum dot.
                      The main degrees of freedom here are fermions. In our limit
                      of interest, we do not resolve coherences in the description
                      of the dynamics and determine the kernel of the
                      time-evolution operator based on Fermi’s Golden rule and
                      the electrostatics of the device. In spite of this
                      simplification, we show that it is still advantageous to
                      formulate the traditional approach in Liouville space to
                      study the transient dynamics instead of the stationary
                      state. In the large gap limit, we make use of a dissipative
                      symmetry, termed fermionic duality, that refers to a
                      generalized hermiticity relation of the time-evolution
                      kernel. The duality leads to non-trivial relations between
                      the quantities that determine the state and transport
                      evolution. It is then the duality that further facilitates
                      the analysis, as the transient behavior of the quantum dot
                      can be understood in great detail in terms of stationary
                      quantities of the real and dual system. In particular the
                      heat current is an interesting transport observable, as it
                      probes the interplay of Coulomb interaction and
                      superconducting pairing. Based on a microscopic
                      understanding of the underlying processes, we describe how
                      to control the charge and heat currents in these NDS-devices
                      by a suitable choice of the parameters. We give outlooks to
                      further extensions of our approach to quantum dots attached
                      to two superconductors, which promise interesting physics
                      both from a theoretical and experimental perspective.},
      cin          = {135110 / 130000},
      ddc          = {530},
      cid          = {$I:(DE-82)135110_20140620$ / $I:(DE-82)130000_20140620$},
      pnm          = {GRK 1995 - GRK 1995: Quantenmechanische
                      Vielteilchenmethoden in der kondensierten Materie
                      (240766775)},
      pid          = {G:(GEPRIS)240766775},
      typ          = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
      doi          = {10.18154/RWTH-2023-06360},
      url          = {https://publications.rwth-aachen.de/record/960727},
}