Non-Markovian Spontaneous Emission Dynamics of a Quantum Emitter Near a Transition-Metal Dichalcogenide Layer

We investigate the spontaneous emission dynamics of a two-level quantum emitter near a transition-metal dichalcogenide layer, specifically, a tungsten disulfide (WS2) layer. The optical response of the WS2 layer is obtained by electromagnetic calculations using parameters by experimental data. We find that depending on the distance between the quantum emitter, and the WS2 layer the spontaneous decay can be enhanced up to 10(4) compared with its free-space value for an emitter with transition dipole moment oriented perpendicular or tangential to the layer. We also perform quantum dynamical calculations, which indicate that the emitter's spontaneous emission dynamics changes from Markovian to weakly non-Markovian to clearly non-Markovian, featuring decaying population oscillations, as the coupling grows from relatively weak to strong, depending on the distance of the emitter to the layer, and the emitter's free-space decay rate. For quantum emitters with fast free-space decay times placed at close distances to the WS2 layer, the ultrastrong coupling regime can be reached, and we find that a significant amount of the initial population of the quantum emitter can remain trapped in it. We also quantify non-Markovianity using different measures. Similar results can also be obtained for other transition-metal dichalcogenide layers, like a tungsten diselenide (WSe2) layer.