Spin noise reveals spin dynamics and recharging of lead halide perovskite nanocrystals

TL;DR

This study uses spin noise spectroscopy to investigate spin dynamics, recharging, and optical effects in lead halide perovskite nanocrystals embedded in glass, revealing long-lived spin coherence and light-induced charge recharging phenomena.

Contribution

It introduces a novel application of spin noise spectroscopy to lead halide perovskite nanocrystals, uncovering spin properties, recharging mechanisms, and optical magnetic field effects.

Findings

Record spin dephasing time of 2.7 ns for resident electrons.

Persistent hole recharging observed after illumination.

Optical magnetic field induced by elliptically polarized light.

Abstract

The lead halide perovskite nanocrystals embedded into a glass matrix exhibit strong interaction with light and demonstrate exceptional optical and spin related features along with long-term chemical and physical stability. We apply the spin noise spectroscopy technique which offers a number of specific opportunities to study the spin system of CsPbI$_3$ nanocrystals in a fluorophosphate glass matrix. A pronounced spin precession peak with an isotropic $g$-factor absolute value of 2.7 and record dephasing time of T$_{2\text{,e}}$ = 2.7 ns is ascribed to resident electrons in the perovskite nanocrystals. The experimentally observed Faraday rotation noise with no noise of ellipticity is explained by saturation of the inhomogeneously broadened optical transition. Increasing the probe intensity, we went beyond the non-perturbative regime and observed a number of light-induced effects. In particular, the illumination with shorter wavelength light gives rise to a persistent recharging of the quantum dots by holes ($|g|=0.17$ and T$^*_{2\text{,h}}$ = 1.4 ns, T$^*_{1\text{,h}}$ $\geq$ 30 ns), which remains stable over multiple cycles of heating to the room temperature and cooling. In addition, elliptically polarized light induced an "optical" magnetic field on the system due to the AC Stark effect. It is confirmed using a new modification of polarization noise spectroscopy with a small degree of circular polarization of the probe light added with different frequencies.