Assessing the classicality of photon echo from excitons in lead halide perovskite nanocrystals

TL;DR

This study uses photon echo spectroscopy and quantum state tomography to analyze exciton coherence and photon statistics in lead halide perovskite nanocrystals, revealing classical photon behavior despite complex energy structures.

Contribution

It demonstrates the application of homodyne detection to assess photon statistics of PE signals in perovskite nanocrystals, showing classical behavior with minimal noise.

Findings

Photon echo signals exhibit classical Poissonian photon statistics.

Damping of Rabi oscillations is due to excitation inhomogeneity and dephasing.

Despite low efficiency, PE signals maintain high coherence and classical photon behavior.

Abstract

Photon echo (PE) spectroscopy is a powerful technique for probing decoherence mechanisms and charge carrier dynamics in semiconductor systems. Beyond traditional coherence measurements, characterizing the photon statistics of the echo signal is important for assessing its potential in quantum information applications and understanding the underlying quantum mechanical processes. Here, we study the photon statistics of PE signals generated by excitons in ensembles of lead halide perovskite CsPbI$_3$ nanocrystals at cryogenic temperature of 2 K using continuous-variable quantum state optical tomography based on homodyne detection. Pronounced Rabi oscillations of PE amplitude allow us to evaluate the statistics for various pulse areas in the excitation sequence. The damping of the oscillations with increasing pulse area is attributed to spatial excitation inhomogeneity and excitation-induced dephasing. Despite the large ensemble of optically addressed excitons, the efficiency of generated PE signals is low which is attributed to complex energy structure of excitons and non-radiative recombination channels in CsPbI$_3$ nanocrystals. We analyze the statistical characteristics of PE via the second-order correlation function $g^{(2)}(0)$ and the characteristic function for different combinations of the areas of the excitation pulses. Our results show that $g^{(2)}(0) = 1$, and the characteristic function of the PE signal corresponds to classical behavior. Despite the relatively low efficiency, the photon echo exhibits a high degree of coherence and minimal classical noise, consistent with Poissonian statistics.