123893 20230914083805.0 doi 10.21468/SciPostPhysLectNotes.50 sideral 132314 ART-2022-132314 eng Román-Roche, Juan (orcid)0000-0003-2995-6615 Effective theory for matter in non-perturbative cavity QED 2022 Access copy available to the general public Unrestricted Starting from a general material system of N particles coupled to a cavity, we use a coherent-state path integral formulation to produce a effective theory for the material degrees of freedom. We tackle the effects of image charges, the A^2 term and a multimode arbitrary-geometry cavity. The resulting (non-local) action has the photonic degrees of freedom replaced by an effective position-dependent interaction between the particles. In the large-NN limit, we discuss how the theory can be cast into an effective Hamiltonian where the cavity induced interactions are made explicit. The theory is applicable, beyond cavity QED, to any system where bulk material is linearly coupled to a diagonalizable bosonic bath. We highlight the differences of the theory with other well-known methods and numerically study its finite-size scaling on the Dicke model. Finally, we showcase its descriptive power with three examples: photon condensation, the 2D free electron gas in a cavity and the modification of magnetic interactions between molecular spins; recovering, condensing and extending some recent results in the literature. info:eu-repo/grantAgreement/ES/CSIC/PTI-001 info:eu-repo/grantAgreement/ES/DGA/E09-17R-Q-MAD info:eu-repo/grantAgreement/EC/H2020/862893/EU/Molecular spin qudits offering new hope for quantum computing/FATMOLS This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No H2020 862893-FATMOLS info:eu-repo/grantAgreement/ES/MICINN-AEI/PID2020-115221GB-C41 info:eu-repo/semantics/openAccess by http://creativecommons.org/licenses/by/3.0/es/ 9.1 2022 info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion Zueco, David (orcid)0000-0003-4478-1948 50 (2022), [32 pp.] SciPost Phys. Lect. Notes SciPost Physics Lecture Notes 2590-1990 841305 http://zaguan.unizar.es/record/123893/files/texto_completo.pdf Versión publicada 1898289 http://zaguan.unizar.es/record/123893/files/texto_completo.jpg?subformat=icon icon Versión publicada oai:zaguan.unizar.es:123893 articulos driver 2023-09-13-15:23:49 ARTICLE