A new look at spectral fluctuations in single colloidal quantum dots at cryogenic temperatures

Abstract

Thanks to their high tunability and ease of integration into microstructured devices, colloidal quantum dots (CQDs) have become a widespread building block in electro-optic technology. In order to translate this success into the realm of quantum science and technology, spectral stability and coherence, two closely linked topics, need to be addressed. In this talk, I will describe our recent effort in answering one of the fundamental questions in this regard: what is the underlying cause of spectral noise in the emission of CQDs? We embed CdSe/CdS core/shell quantum dots into microcapacitors and perform high-resolution photoluminescence spectroscopy of individual nanoparticles at cryogenic temperatures. Applying an external electric bias, we shift their emission wavelength and its sensitivity to spurious electric fields. Increasing this sensitivity, we observe a clear emhancement in the dynamic variance of the energy of the emitted photons. Fitting this result to a straightforward model, we provide direct evidence that microscopic stochastic electric fields are the root cause of spectral fluctuations in CQDs.