Coupling of Quantum-Well Excitons to Plasmons in One-Dimensional Metal Nanocylinder Gratings
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XVIII INTERNATIONAL SYMPOSIUM “NANOSTRUCTURES: PHYSICS AND TECHNOLOGY”, MINSK, REPUBLIC OF BELARUS, SEPTEMBER, 2020. EXCITONS IN NANOSTRUCTURES
Coupling of Quantum-Well Excitons to Plasmons in OneDimensional Metal Nanocylinder Gratings A. V. Korotchenkov* Ioffe Institute, St Petersburg, 194021 Russia *e-mail: [email protected] Received July 24, 2020; revised July 24, 2020; accepted July 24, 2020
Abstract—Theory of plasmon-exciton coupling is developed for a metal nanocylinder grating located in the vicinity of a semiconductor quantum well. In dipole approximation, the effective polarizability of cylinders is derived, taking into account generation of quantum-well excitons in the near field of surface plasmons. Given the polarizability, the spectra of reflection and absorption are calculated for metal-semiconductor systems to study the effect of plasmon-exciton interaction. The excitonic response is shown to be enhanced by highquality plasmons of Ag cylinders, although strong coupling is not attained for realistic nanostructure parameters. Keywords: plasmon-exciton coupling, nanostructures, metal nanocylinders, resonance splitting DOI: 10.1134/S1063782620110159
1. INTRODUCTION
demonstrate the excitonic features to be enhanced when in resonance with plasmons.
Plasmons in metal nanostructures have proved useful in numerous optical applications due to localization of electromagnetic field on nanometer scale. Recently, considerable attention has been drawn to the coupling between excitons in organic molecules and surface plasmons in metal nanoparticles. In such systems hybrid excitations called plasmon-excitons can occur, manifesting themselves in anticrossing in resonant scattering and luminescence spectra, as discussed in review [1]. Interaction of excitons in solids with plasmons has been studied as well, both in theory [2] and by experiment. An evidence for plasmon-exciton coupling has been obtained for a few metal-semiconductor structures including semiconductor quantum wells, see [3] for example. While numeric simulations were employed to explore the plasmon resonances and match them to the exciton frequencies in particular structures, an elementary model is yet required to estimate the magnitude of coupling effects. This theoretic paper studies the coupling of quantum-well (QW) excitons and plasmons in metal nanocylinder (NC) grating. Based on electrodynamic model of [2], we consider the near-field interaction between NC plasmons and low-dimensional excitons. As a result, the cylinders are characterized by the resonant effective polarizability, from which the plasmon-exciton coupling strength is obtained. Then, we calculate the reflection and absorption spectra and
2. MODEL A grating of metal NC is considered, embedded in semiconductor material with background permittivity εb in the vicinity of a QW (Fig. 1). The size of NC cross-section, the grating period and the distance between the cylinders and QW are assumed to be subwavelength. In absence of NCs, two-dimensional excitons cause resonances in th
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