Memory in quantum-dot photoluminescence blinking

We demonstrate that subsequent on- and off-times of the luminescence blinking of semiconductor quantum dots (QDs) are correlated, indicating that the process behind is not memoryless. A residual memory, which has been overlooked in previous investigations of the blinking, is found to last for several (~40) detected on/off cycles. No influence of the substrate nature or the excitation intensity is observed, pointing to a process intrinsic to the QDs. These results should encourage re-analysis of existing data and may represent the key to understand the underlying physical mechanism of QD luminescence blinking.