Spectral shadows of a single GaAs quantum dot

TL;DR

This study provides detailed insights into the spectral shifts and charge dynamics of a single GaAs quantum dot, revealing impurity effects, charge state fluctuations, and the impact of auxiliary lasers on hole occupancy.

Contribution

It introduces a comprehensive analysis of spectral shadows and charge dynamics in a single quantum dot using resonance fluorescence and spin noise spectroscopy.

Findings

Multiple Stark-shifted resonances linked to impurity environment.

Charge dynamics vary from milliseconds to seconds, affecting hole occupation.

Non-resonant laser increases hole occupancy and modifies tunneling rates.

Abstract

Semiconductor quantum dots are a promising platform for generating single and entangled photons.Still, their use is limited even in the most advanced structures by changes in the charge state of the quantum dot and its environment. Here, we present detailed time-resolved resonance fluorescence measurements on a single charge-tunable GaAs quantum dot, shedding new light on the spectral shadows invoked by the complex impurity environment. Detuning-dependent measurements reveal the existence of multiple Stark-shifted resonances, which are associated with rare spectral jumps smaller than the homogeneous linewidth and, therefore, typically concealed in the measurement noise. We observe similar environmentally induced Stark shifts for both the neutral exciton and negatively charged trion transitions, while the positively and doubly negatively charged trions exhibit significant differences. Our investigation quantifies the underlying impurity charge dynamics over a range from well below milliseconds to seconds, revealing that the hole occupation of the positively charged trion transition is constrained by rapid hole loss and slow hole recapture dynamics. Utilizing a second non-resonant laser, we increase the hole occupancy by over an order of magnitude and identify both a prolonged hole residence time and an enhanced hole tunneling rate into the quantum dot. These findings are supported by complementary spin noise spectroscopy measurements, which offer a significantly higher bandwidth compared to the time-resolved resonance fluorescence measurements.