Anomalous Power Laws of Spectral Diffusion in Quantum Dots: A Connection to Luminescence Intermittency

Abstract

We show that the wandering of transition frequencies in colloidal quantum dots does not follow the statistics expected for ordinary diffusive processes. The trajectory of this anomalous spectral diffusion is characterized by a ffiffi t p dependence of the squared deviation. The behavior is reproduced when the electronic states of quantum dots are assumed to interact with environments such as, for example, an ensemble of two-level systems, where the correlation times are distributed according to a power law similar to the one generally attributed to the dot's luminescence intermittency.

Cryogenic Single-Nanocrystal Spectroscopy: Reading the Spectral Fingerprint of Individual CdSe Quantum Dots

“…Spectral diffusion causes rapid decoherence of individual quantum states and currently limits the ability to use coherent control techniques with these materials. This is currently attributed to surface instabilities, most likely associated with the surface ligands 15,16 . A number of possible routes to achieving stable emission exist, the most direct being using thicker shells to reduce the influence of the surface.…”

“…Subsequent studies of spectral diffusion revealed it to be photophysical in origin as distinct dependencies on the pumping wavelength and power were reported 12 . Cryogenic spectroscopy of single NCs has since yielded intimate detail of the photophysics underlying spectral diffusion [13][14][15][16] , which is illustrative of its importance as a tool for probing the complex photophysics of NC materials.…”

Photon-correlation Fourier spectroscopy of the trion fluorescence in thick-shell CdSe/CdS nanocrystals

“…Trapping and movements of charges at the shell-ligands interface result in fluctuations of the local electric field that induce random spectral jumps and broaden the emission linewidth. The dynamics of the SD has received great interest [11][12][13][14] since it limits the use of colloidal NC in applications such as two-photon interference * jean-pierre.hermier@uvsq.fr in the domain of quantum computing for which time coherence is a key point. SD can be studied using either conventional spectroscopic technique, which is based on the acquisition of consecutive photoluminescence (PL) spectra [13], or by more advanced methods.…”

Excited-State Dynamics in Colloidal Semiconductor Nanocrystals

“…Temporal variations in the peak emission wavelength are accompanied by, and correlated with, variations in the emission line width [285][286][287][288]. Most of the experiments into spectral diffusion were conducted at cryogenic temperatures [289][290][291][292], but the process occurs at room temperature, too [285][286][287][288]. A direct link between spectral diffusion and blinking was proposed, based on correlations between blinking events (on-off switches) and spectral shifts [290,293].…”