We study the interaction between a topological insulator nanoparticle and a quantum dot subject to an applied electric field. The electromagnetic response of the topological insulator is derived from axion electrodynamics in the quasistatic approximation. Localized modes are quantized in terms of dipolar bosonic modes, which couples dipolarly to the quantum dot. Hence, we treat the hybrid as a two-level system interacting with a single bosonic mode, where the coupling strength encodes the information concerning the nontrivial topology of the nanoparticle. The interaction of the hybrid with the environment is implemented through the coupling with a continuum reservoir of radiative output modes and a reservoir of phonon modes. In particular, we use the method of Zubarev's Green functions to derive an expression for the optical absorption spectrum of the system. We apply our results to a realistic system which consists of a topological insulator nanoparticle made of TlBiSe2 interacting with a cadmium selenide quantum dot, both immersed in a polymer layer such as poly(methyl methacrylate). The optical absorption spectrum exhibits Fano resonances with a line shape that strongly depends on the polarization of the electric field as well as on the topological magnetoelectric polarizability θ. Our results and methods can also be applied to nontopological magnetoelectric materials such as Cr2O3.

We investigate the interaction between a topological insulator nanoparticle and a quantum dot in an impulse magnetic field. Since topological insulators are nonmagnetic, after the impulse has ended only the localised topological surface modes, which are quantised in terms of dipolar bosonic modes, thus coupling dipolarly to the quantum dot. Hence, the hybrid system can be treated as a single bosonic mode interacting with a two-level system, where the coupling strength is quantised in terms of the magnetoelectric polarizability. We implement the interaction of the hybrid with the environment through the coupling with a continuum reservoir of radiative output modes and a reservoir of phonon modes. Using the method of Zubarevs Green functions, we derive an expression for the optical absorption spectrum of the system. We find the emergence of Fano resonances which are direct manifestations of the Z2 invariant of topological insulators. We present numerical results for a topological insulator nanosphere made of TlBiSe2 interacting with a CdSe quantum dot.

In the present work, we consider a hybrid plexciton composed of a semiconductor quantum dot interacting with a topological insulator nanoparticle subject to an external magnetic field. Due to the topological magnetoelectricity of the nanoparticle, long-living plasmonic surface modes are induced, which are quantized and coupled with the quantum dot through its polarization operator. We consider the hybrid as an open quantum system, such that environment effects are accounted by the master equation in the Born–Markov approximation. Then, we apply the Peres’ positive partial transpose criterion to quantify the entanglement of the hybrid. We show that this entanglement is a direct signature of the $$\mathbb {Z}_2$$ Z 2 invariant of topological insulators.