Multi-Dimensional Photon-Correlations Reveal Triexciton Features in Single Perovskite Quantum Dots

Abstract: Lead-halide perovskite quantum dots (PQDs) are established quantum emitters with potential for entangled photon-pair generation via multiexciton cascades. However, the energetics and dynamics of many-body excitations remain poorly understood. Here, we perform time- and frequency-resolved photon-correlation spectroscopy of single CsPbBr\textsubscript{3} PQDs at low temperatures using a single-photon avalanche diode (SPAD) array detector. We report biexciton binding energies and assign their charged states, which undergo fast ($\mu$s) switching dynamics. Most notably, we identify a spectral feature blue-shifted from the exciton by $7.4 \pm 1.9$ meV as the bound triexciton and establish the order of its cascade emission. These results highlight the power of low-temperature, multidimensional photon-correlation spectroscopy for resolving complex many-body dynamics.