Polarization of photoluminescence by optically driven orbital reconstruction in magnetically ordered CrCl3

TL;DR

This study demonstrates that magnetization and strain in CrCl3 influence its photoluminescence polarization, with DFT calculations revealing orbital and spin reconfigurations upon photon absorption.

Contribution

It provides new insights into how magnetic order and orbital reconstruction affect photoluminescence polarization in CrCl3, combining experimental and theoretical approaches.

Findings

Photoluminescence exhibits polarization dependence on magnetic order and strain.

Magnetization influences orbital occupation and spin orientation in CrCl3.

DFT calculations show electron excitation causes orbital magnetic moments and lattice deformation.

Abstract

In this paper, we show that photoluminescence from CrCl3 bulk crystal exhibits a preferential polarization direction when films are magnetically ordered or strained. We verify the magnetization as responsible for the polarization by measuring the signal as a function of the temperature in Voigt configuration while applying the in-plane magnetic field. We show that phonon coupling contributing to vibronic transitions depolarizes the signal compared with zero phonon lines. We explain the data using DFT calculations, which reveal a magnetization-selective occupation of the low energy d-orbital triplet state of Cr3+ upon photon absorption. In addition, the calculations find that the excitation of one electron results in the excited state acquiring out-of-plane components of spin and very large orbital magnetic moments, in addition to a lattice deformation.