Electrical Routing of Dipole Decay Between Radiative and Nonradiative Channels via Graphene Plexcitons

ABSTRACT

We investigate the electrical control of a dipole decay rate near a quantum dot coated with a graphene spherical shell. The optical response and decay rates are calculated from 3D Maxwell equations using the boundary element method. We first examine the strong‐coupling condition. The upper and lower hybrid branches show a clear avoided crossing, and a coupled‐oscillator fit gives a minimum splitting of . The large modulation of the total rate originates mainly from the nonradiative LDOS. At the plexcitonic resonances, the normalized nonradiative rate approaches , whereas the radiative rate remains unchanged. At a fixed emitter wavelength of , changing the graphene chemical potential modifies the nonradiative rate from 37 to 920, corresponding to a 24‐fold modulation (14 dB). To explain the results, we develop a non‐Hermitian coupled‐mode model showing how the plasmonic and excitonic contents, the linewidths of two branches, and the detuning. It also predicts a dispersive frequency shift accompanying the decay‐rate modulation. These results show that the graphene‐quantum‐dot system provides two electrically tunable decay channels rather than a large radiative Purcell enhancement.