Elementary excitations in charge-tunable InGaAs quantum dots studied by resonant Raman and resonant photoluminescence spectroscopy

摘要

We report on resonant optical spectroscopy of self-assembled InGaAs quantumdots in which the number of electrons can accurately be tuned to N=0,1,2 by anexternal gate voltage. Polarization, wave vector and magnetic field dependentmeasurements enable us to clearly distinguish between resonant Raman andresonant photoluminescence processes. The Raman spectra for N=1 and 2 electronsconsiderably differ from each other. In particular, for N=2, the quantum-dotHe, the spectra exhibit both singlet and triplet transitions reflecting theelementary many-particle interaction. Also the resonant photoluminescencespectra are significantly changing by varying the number of electrons in theQDs. For N=1 we observe strong polaronic effects which are suppressed for N=2.