The role of exchange interactions in superradiant phenomena

Abstract: The Dicke model is a central platform for exploring strong light-matter interaction and its superradiant properties, with implications for emerging quantum technologies. Recognizing that realistic qubits inherently experience direct interactions, we investigate the influence of both isotropic and anisotropic spin-spin couplings on the Dicke paradigm. In the strong coupling regime--where large photon populations challenge conventional numerical techniques--we developed a hybrid numerical method tailored for this problem, which demonstrates high accuracy and rapid convergence in reproducing established Dicke model results. Furthermore, our study reveals that distinct ferromagnetic and antiferromagnetic regions exhibit different orders of phase transitions. Most notably, in the presence of anisotropic interactions, we identify a novel phase where spin order and superradiance coexist, marked by enhanced superradiance with a photon number significantly exceeding that of the conventional Dicke model.