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TY - THES AU - Eckhardt, Christian Johannes TI - Cavitronics in low-dimensional systems PB - RWTH Aachen University VL - Dissertation CY - Aachen M1 - RWTH-2024-05146 SP - 1 Online-Ressource : Illustrationen PY - 2024 N1 - Veröffentlicht auf dem Publikationsserver der RWTH Aachen University N1 - Dissertation, RWTH Aachen University, 2024 AB - Controlling material properties with light is a tantalizing goal of modern condensed matter physics. As a novel path to achieve this goal placing materials into optical cavities, effectively hybridizing light and matter degrees of freedom, has been put forward recently. In this thesis we explore the potential of such cavity engineering for low dimensional electronic systems – hence the term cavitronics. To this end we propose a minimal model for cavitronics. It accounts for the change of the electromagnetic field inside a cavity by coupling the electrons to a single bosonic mode in analogy to paradigmatic models in the related field of quantum optics. We find the exact ground state of the model and identify observables that allow the verification of strong coupling between the electrons and the photons of the cavity in spectroscopy or conductivity measurements. In a next step, we investigate the validity of single-mode models in the context of cavitronics. For this purpose we compute the mass change of itinerant electrons in different cavity setups taking the full continuum of modes of the electromagnetic field into account. Our results indicate the validity of a single mode approximation for describing the electromagnetic field confined in surface modes, such as in the case of surface phonon-polaritons. They further provide a recipe for obtaining the phenomenological light-matter coupling to that single mode. Extending our previous model to an interacting one, we analyze light-matter hybridization between electronic systems and photons in a cavity. We identify specific quantum fluctuations of the matter system to play a pivotal role for achieving such hybridization. As a concrete application we explore the propensity of an optical resonator to induce or enhance super-conductivity. We investigate how the hybridization of optically active phonons with the photons of a cavity, forming phonon-polaritons, affects their potential to mediate an effective attraction between the electrons. As an orthogonal route, we put forward a novel mechanism for photo-induced superconductivity. This mechanismis based on weak driving of a boson, such as a photon inside a cavity, coupling to an electronic transition. We propose a concrete and realizable experimental setup to test our predictions consisting of a cavity that confines light in a surface mode coupled to the two-dimensional material graphene. Through these points our work contributes to pushing the field of cavitronics towards concrete experimental realizations in a three-fold manner: (i) It establishes basic phenomenology of cavitronics in minimal models; (ii) connects these models to a realistic treatment of the electromagnetic field in order to identify ideal cavity setups; and (iii) makes experimentally testable predictions. LB - PUB:(DE-HGF)11 DO - DOI:10.18154/RWTH-2024-05146 UR - https://publications.rwth-aachen.de/record/986309 ER -