In situ charge detection with single Quantum Dot Molecules

Excitons hosted in quantum dot molecules (QDMs) present unique opportunities to directly investigate the physics of interacting quantum states at the single-charge scale. These systems are highly sensitive to small fluctuations in the local environment, making them suitable for in situ nano-scale monitoring. We describe the predicted spectral patterns of a single QDM under the influence of nearby charge states for the spatially direct and indirect neutral excitons and propose a means to utilize the trion state to break symmetry and distinguish between positive and negative charges. Under lifetime-limited conditions, we calculate that the indirect exciton demonstrates μm-scale single charge sensitivity. Using electric-field dispersed photoluminescence spectroscopy, we observe splittings in the emissions of several epitaxially-grown InAs/GaAs QDMs embedded in nipip diode samples that demonstrate strong consistency with predictions and indicate the presence of single charge interactions at distances of up to 100nm.