Heralded spectroscopy reveals exciton-exciton correlations in single colloidal quantum dots

TL;DR

This paper introduces a novel room-temperature spectroscopy technique for single colloidal quantum dots, enabling direct observation of exciton-exciton interactions and revealing correlations masked in ensemble measurements.

Contribution

The authors develop biexciton heralded spectroscopy using a single-photon avalanche diode array, allowing direct measurement of biexciton binding energy at room temperature.

Findings

Direct measurement of biexciton binding energy below thermal broadening.

Observation of correlations between biexciton binding energy and local electrostatic potential.

Potential for advancing charge-carrier dynamics understanding and quantum optics protocols.

Abstract

Multiply-excited states in semiconductor quantum dots feature intriguing physics and play a crucial role in nanocrystal-based technologies. While photoluminescence provides a natural probe to investigate these states, room temperature single-particle spectroscopy of their emission has so far proved elusive due to the temporal and spectral overlap with emission from the singly-excited and charged states. Here we introduce biexciton heralded spectroscopy, enabled by a single-photon avalanche diode array based spectrometer. This allows us to directly observe biexciton-exciton emission cascades and measure the biexciton binding energy of single quantum dots at room temperature, even though it is well below the scale of thermal broadening and spectral diffusion. Furthermore, we uncover correlations hitherto masked in ensembles, of the biexciton binding energy with both charge-carrier confinement and fluctuations of the local electrostatic potential. Heralded spectroscopy has the potential of greatly extending our understanding of charge-carrier dynamics in multielectron systems and of parallelization of quantum optics protocols.