Temperature dependence of the zero-phonon linewidth in quantum dots:: An effect of the fluctuating environment

We report systematic measurements on the broadening of the emission spectrum of single quantum dots as a function of temperature and incident power. Spectral diffusion effects in the motional narrowing regime provide a quantitative interpretation of our experimental results. We show that, at low incident power, the thermal activation of spectral diffusion results in a Lorentzian zero-phonon line with a width that increases linearly with temperature. Our study provides a unified interpretation to the widely debated issue of the dispersion of the data on the temperature dependence of this zero-phonon linewidth. Our explanation is based on an original model where acoustic phonons interact with carriers outside the quantum dot.