Land\'e g-factors and spin dynamics of charge carriers in CuCl nanocrystals in a glass matrix

TL;DR

This study investigates the spin properties and Landé g-factors of charge carriers in CuCl nanocrystals of various sizes, combining experimental measurements with theoretical modeling to understand size-dependent spin dynamics and exciton behavior.

Contribution

It provides a comprehensive experimental and theoretical analysis of spin and exciton properties in CuCl nanocrystals, including a new model for size-dependent Landé g-factors in spherical semiconductor nanocrystals.

Findings

Electron g-factor close to 2, weakly increasing with decreasing nanocrystal size.

Theoretical explanation of exciton energy size dependence via heavy hole-light hole mixing.

Parameters of the six-band Hamiltonian estimated from experimental data.

Abstract

The spin properties of charge carriers confined in CuCl semiconductor nanocrystals (NCs) of different sizes (radius from 1.8 nm up to 28 nm) crystallized in a glass matrix are studied experimentally and theoretically. By means of photoluminescence, spin-flip Raman scattering, time-resolved Faraday ellipticity, and time-resolved differential transmission performed at temperatures in the range of $1.6 - 120$ K at magnetic fields up to 8 T, comprehensive information on the Land\'e $g$-factors as well as the population and spin dynamics is received. The spin signals are contributed by confined electrons with a $g$-factor close to 2, which shows a weak increase with decreasing NC size, i.e. increasing electron confinement energy. We revisit the theory of exciton confinement as a whole in spherical NCs within the six-band valence band model in order to describe the size dependence of the $Z_3$ and $Z_{1,2}$ exciton energies in CuCl NCs. We demonstrate theoretically that the stronger increase of the $Z_{1,2}$ energy transitions with decreasing radius can be explained by the strong absorption from the excited exciton state caused by strong heavy hole-light hole mixing in the exciton. The parameters of the six-band Hamiltonian describing both the exciton and hole kinetic energies are estimated from the comparison of the calculated and experimental size dependences of the exciton transitions. A theoretical model of the size-dependent Land\'e $g$-factors for electron and hole confined in spherical NCs of semiconductors with negative spin-orbit splitting of the valence band is developed.