PHYSICAL REVIEW A 100, 013817 (2019) Modification of a plasmonic nanoparticle lifetime by coupled quantum dots Ahmad Salmanogli Faculty of Engineering, Electrical and Electronics Engineering Department, Çankaya University, Ankara, Turkey (Received 18 December 2018; published 10 July 2019) In this study, the interaction between a plasmonic nanoparticle and coupled quantum dots is investigated to identify how the coupled particles can manipulate the plasmonic nanoparticle decay rate. This subject is very important, because most applications of the plasmonic system are restricted due to the nanoparticle decay rate and the related losses. Therefore, in the present work, we try to find out how and by which method the plasmonic nanoparticle decay rate can be manipulated. For this purpose, a plasmonic system containing a nanoparticle coupled to some small quantum dots is designed. The system dynamics of motions are analyzed with Heisenberg- Langevin equations. These equations are analyzed to study the effect of the plasmonic nanoparticles on the quantum dots’ decay rate. In the following, as an interesting point, the quantum dot coupling influence on the nanoparticle’s decay rate is theoretically analyzed in the transient and steady-state conditions. Additionally, a theoretical formula is derived by which one can explicitly find the dependency of the modified decay rate of the plasmonic nanoparticle on the number of the coupled quantum dots and the coupling strength. The simulation results show that it is possible to effectively control the nanoparticles’ decay rate with regard to the application for which they are utilized. DOI: 10.1103/PhysRevA.100.013817 I. INTRODUCTION Recently, the plasmonic effect has been widely utilized in different applications such as highly sensitive sensors [1,2], quantum imaging [3], imaging filters [4,5], imaging resolution enhancing [6], sensitive plasmonic-photonic nanosensors [7], and Raman signal enhancing [8]. In general, plasmonic prop- erty refers to harmonious oscillating of the surface charges of noble metal interacting with the incident wave [9–11]. By interaction of an incident wave with a metal, an intense field is generated close to the surface where the interaction took place. This field is known as the plasmonic field and, in most applications, is utilized as same role as the radio-frequency antenna to amplify the incident wave [12,13]. It has been reported that the plasmonic field is efficiently coupled to any small particles such as quantum dots (QDs) embedded at the region’s so-called hot spot [9,10]. The coupling of the plasmonic nanoparticle (NP) to QDs has been applied because of the above-mentioned advantages, which suggest that the optical properties of the system (NP-QDs) are changed by considering the coupling effects. This alteration due to the coupling effect is a critical case in numerous applications such as in sensory applications [4–8]. Due to the important role of the plasmonic field, several studies have been conducted on plasmonic field engineering using nanotechnology to convert the plasmonic field to the lattice plasmonic field [5,14]. In this case, the plasmonic field operates as a laser with a high- intensity field and very narrow bandwidth. However, in this article, we focus on the interaction of the plasmonic NP with QDs, and it is shown how the coupled sys- tem’s optical properties can be manipulated. Accordingly, it is found that some intrinsic properties of the coupled particles such as NP’s decay rates are altered. The NP’s plasmonic field effect on the QDs’ decay rate (i.e., the Purcell factor) has been studied in recently published works [9,10]. It has been proved that the NP-QDs’ interdistance changing manipulates the coupling strength between the NP and the QDs, then, leading to dramatic changing in the QDs’ decay rates. Additionally, in some interesting works, the NPs coupling to the QDs’ spacer has been theoretically and experimentally investigated [15–17]. In [15], the authors proposed a way to excite the local field using plasmon resonance through spacer radiation. This radiation has a unique ability, in contrast to photons, such that it can be localized on the nanoscale. Therefore, it can be imagined as the plasmon resonance squeezed state. The latter important property has been deeply investigated [18], indicating that the plasmonic mode can be squeezed into a volume far below the diffraction limit. Another interesting work studied the spacer as a nanoscale quantum amplifier in which the spacer can be function as an ultrafast nanoamplifier [16]. The main problem of the spacer, which is the inherent feedback, is the quantum generation of localized surface plas- mon and eliminating the net gain. This issue has contributed to the plasmonic field effect on the QDs’ transition rates. However, all the similar studies in the case of the spacer have investigated either the effect of the NPs’ plasmonic field on the QDs’ optical properties or the QDs’ effect on the local- ized field close to the NPs. Meanwhile, it seems that it should be necessary to study the effect of the QDs’ coupling strength on the NP decay rate. The most interesting point of this study is that the decrease of the NP’s decay rate strongly enhances the plasmonic applications; for instance, plasmon resonance mode entanglement [4,18,19] can be largely improved due to the plasmonic mode lifetime increasing. Therefore, in this article, it is theoretically shown that the QDs attached can dramatically modify the NP’s decay rate. Notably, we just focus on the hot-spot region where the QDs are embedded. This region is the area where the plasmonic field is maximized 2469-9926/2019/100(1)/013817(8) 013817-1 ©2019 American Physical Society