Electric-Field Fluctuations as the Cause of Spectral Instabilities in Colloidal Quantum Dots

Abstract

Spectral diffusion (SD) represents a substantial obstacle toward implementation of solid-state quantum emitters as a source of indistinguishable photons. By performing highresolution emission spectroscopy for individual colloidal quantum dots at cryogenic temperatures, we prove the causal link between the quantum-confined Stark effect and SD. Statistically analyzing the wavelength of emitted photons, we show that increasing the sensitivity of the transition energy to an applied electric field results in amplified spectral fluctuations. This relation is quantitatively fit to a straightforward model, indicating the presence of a stochastic electric field on a microscopic scale, whose standard deviation is 9 kV/cm, on average. The current method will enable the study of SD in multiple types of quantum emitters such as solid-state defects or organic lead halide perovskite quantum dots, for which spectral instability is a critical barrier for applications in quantum sensing.

Suppressed Magnitude of Spectral Diffusion in Cube-Shaped CdSe/CdS Core/Shell Nanocrystals with Exceedingly Stable Photoluminescence

“…As illustrated in Figure S19, pulsed excitation methods often introduce many instability issues, making CW light excitation a more suitable choice for minimizing spectral diffusion. Near-resonant excitation is another way that may further mitigate spectral diffusion. , Furthermore, applying an appropriate uniform external electric field can aid in mitigating spectral diffusion …”

“…9,38 Furthermore, applying an appropriate uniform external electric field can aid in mitigating spectral diffusion. 39 The ability to observe the phenomena described above relies heavily on the exceptional photophysical and photochemical stability of the nanocrystals. First, the nanocrystals do not become bleached under prolonged irradiation, a requirement for practical applications.…”