G. M. Koutentakis, S. I. Mistakidis, F. Grusdt, H. R. Sadeghpour, P. Schmelcher
SciPost Phys. 19, 093 (2025) ·
published 13 October 2025
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We theoretically investigate the stationary properties of a spin-1/2 impurity immersed in a one-dimensional confined Bose gas. In particular, we consider coherently coupled spin states with an external field, where only one spin component interacts with the bath, enabling light dressing of the impurity and spin-dependent bath-impurity interactions. Through detailed comparisons with ab-initio many-body simulations, we demonstrate that the composite system is accurately described by a simplified effective Hamiltonian. The latter builds upon previously developed effective potential approaches in the absence of light dressing. It can be used to extract the impurity energy, residue, effective mass, and anharmonicity induced by the phononic dressing. Light-dressing is shown to increase the polaron residue, undressing the impurity from phononic excitations because of strong spin coupling. For strong repulsions, previously shown to trigger dynamical Bose polaron decay (a phenomenon called temporal orthogonality catastrophe), it is explained that strong light-dressing stabilizes a repulsive polaron-dressed state. Our results establish the effective Hamiltonian framework as a powerful tool for exploring strongly interacting polaronic systems and corroborating forthcoming experimental realizations.
Vasil Rokaj, Simeon I. Mistakidis, H. R. Sadeghpour
SciPost Phys. 14, 167 (2023) ·
published 22 June 2023
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Cavity quantum electrodynamics provides an ideal platform to engineer and control light-matter interactions with polariton quasiparticles. In this work, we investigate collective phenomena in a system of many particles in a harmonic trap coupled to a homogeneous cavity vacuum field. The system couples collectively to the cavity field, through its center of mass, and collective polariton states emerge. The cavity field mediates pairwise long-range interactions and enhances the effective mass of the particles. This leads to an enhancement of localization in the matter ground state density, which features a maximum when light and matter are on resonance, and demonstrates a Dicke-like, collective behavior with the particle number. The light-matter interaction also modifies the photonic properties of the polariton system, as the ground state is populated with bunched photons. In addition, it is shown that the diamagnetic $A^2$ term is necessary for the stability of the system, as otherwise the superradiant ground state instability occurs. We demonstrate that coherent transfer of polaritonic population is possible with an external magnetic field and by monitoring the Landau-Zener transition probability.
