Hole spin precession and dephasing induced by nuclear hyperfine fields in CsPbBr$_3$ and CsPb(Cl,Br)$_3$ nanocrystals in a glass matrix

TL;DR

This study investigates hole spin dynamics in perovskite nanocrystals within a glass matrix, revealing how nuclear hyperfine interactions influence spin precession and dephasing across various temperatures.

Contribution

It provides the first detailed analysis of nuclear hyperfine effects on hole spins in CsPbBr$_3$ and CsPb(Cl,Br)$_3$ nanocrystals, including quantification of hyperfine interaction energies.

Findings

Pronounced Larmor precession observed in a wide temperature range.

Hole spin dephasing time decreases from 1 ns to 50 ps with temperature.

Hyperfine interaction energy estimated between 2-5 μeV.

Abstract

The coherent spin dynamics of holes are investigated for CsPbBr$_3$ and CsPb(Cl,Br)$_3$ perovskite nanocrystals in a glass matrix using the time-resolved Faraday rotation/ellipticity techniques. In an external magnetic field, pronounced Larmor spin precession of the hole spins is detected across a wide temperature range from 5 to 300 K. The hole Land\'e $g$-factor varies in the range of $0.8-1.5$, in which it increases with increasing high energy shift of the exciton due to enhanced confinement in small nanocrystals. The hole spin dephasing time decreases from 1 ns to 50 ps in this temperature range. Nuclear spin fluctuations have a pronounced impact on the hole spin dynamics. The hyperfine interaction of the holes with nuclear spins modifies their spin polarization decay and induces their spin precession in zero external magnetic field. The results can be well described by the model developed in Ref. 41, from which the hyperfine interaction energy of a hole spin with the nuclear spin fluctuation in range of $2-5$ $\mu$eV is evaluated.