Georgii Semin | Searcharxiv

arXiv2026

Quantum plasmonics with N emitters: bright hybrid continuum selection

We construct mode-selective effective models describing the interaction of the quantum plasmon-polariton field supported by a finite dielectric medium and one or several quantum emitters. The construction of the effective model is based on the decomposition of the field into bright modes relevant to the interaction with the emitters and dark modes, which do not interact with the emitters. We show that the quantum plasmon-polariton field can be represented equivalently by a double-continuum spectrum or by a single hybrid continuum spectrum for each emitter. The system of the electromagnetic field coupled to a finite medium is composed of two families of continuum modes, each of them with an infinite degeneracy. The two families are deformations of the free electromagnetic field and the free medium, induced by the interaction between them, as described by the Lippmann-Schwinger equations. We show that if there are $N$ emitters interacting with this plasmon-polariton field, the effective interaction involves a much smaller set of bosonic continuum modes: the interacting part of the continuum can be described by $N$ non-degenerate one-dimensional continua, one for each emitter. The representation of the interaction in terms of a single hybrid continuum spectrum coincides with the one within the macroscopic Langevin model with bulk medium. This coincidence is explained by an exact compensation of two terms, one in the coupling term of the Hamiltonian and the other one in a Green tensor identity.

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arXiv2025

Three-dimensional canonical quantum plasmonics for finite media: exact solution in terms of the classical Green tensor

This article presents a comprehensive three-dimensional canonical quantization to treat quantum plasmonics for finite metallic or dielectric media of arbitrary shape. We use a microscopic model for the dissipative and dispersive medium coupled with the electromagnetic field, which is justified by the fact that if one integrates the degrees of freedom of the medium, one obtains the macroscopic Maxwell equations. Its quantization features a Hamiltonian formulation having the form of two infinite harmonic oscillators characterized by a double continuum. The diagonalized Hamiltonian is quantized by the correspondence principle, introducing creation-annihilation operators in a bosonic Fock space. The diagonal quantum Hamiltonian is the sum of two terms corresponding to the two continua. The physical observables, like, e.g., the electric field, are also the sum of two terms corresponding to the two continua, one of which had been omitted in the literature geared for an infinite bulk medium. In a second step, we show that the electric field operator can by written as linear combinations of the creation-annihilation operators with coefficients that satisfy integral equations of Fredholm type. We show that the solution of these equations can be expressed in terms of the classical Green tensor of the medium satisfying the Sommerfeld radiation condition. Finally, we consider the Purcell effect for the spontaneous emission of an atom close to the medium. We show that through an exact compensation of some terms, the Purcell factor for the system with the double continuum is proportional to the imaginary part of the Green tensor, which defines the local density of states. This result has the same form as the one obtained in the literature for bulk systems that involve a single continuum and a small dissipative background extending to infinity, and can be seen as a justification of this approach.

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