Quantum Beats in Hybrid Metal−Semiconductor Nanostructures

We investigate nonradiative quantum coherence in the presence of coupling between excitons and surface plasmon polaritons (SPPs) in a hybrid metal−semiconductor nanostructure. In particular, we study how quantum coherence between heavy-hole (HH) and light-hole (LH) excitons in a GaAs quantum well (QW) is modified when they are coupled to SPPs of a gold grating. We find that the nonradative coherence is reduced in correlation with the coupling strength between the excitons and SPPs. Under the resonant coupling condition, the nonradiative coherence remains in the range of hundreds of femtoseconds, which is significantly longer than the plasmonic coherence. These experiments directly probe quantum dynamics in a prototypical hybrid system and provide critical information for exploring future quantum plasmonics applications.