Spontaneous spectral diffusion in CdSe quantum dots

Abstract : Spectral diffusion of the emission line of single colloidal nanocrystals is generally regarded as a purely random process. Here we show that each new spectral position has a finite memory of previous spectral positions, as evidenced by persistent anti-correlations in time series of spectral jumps. The anti-correlation indicates there is a finite probability of the charge distribution around the nanocrystal returning to a previous configuration. We show both statistically and directly that this memory manifests as an observable spontaneous "relaxation" in the absence of a pump laser.