Resonant X-ray spectroscopies on Chromium $3\textit{d}$ orbitals in CrSBr

TL;DR

This study uses resonant x-ray spectroscopies to analyze the electronic structure and excitations of CrSBr, revealing significant dichroism and excitonic features, and develops a crystal field model to interpret these phenomena.

Contribution

The paper introduces a multiplet model based on crystal electric field theory that explains the electronic excitations in CrSBr, highlighting hybridization effects not captured by previous models.

Findings

Significant linear dichroism observed in XAS and RIXS spectra.

Identification of d-d excitations and bright excitons in CrSBr.

The multiplet model reproduces key experimental features and suggests strong hybridization effects.

Abstract

We investigate the Cr electronic structure and excitations in CrSBr, a layered magnetic semiconductor, using a combination of resonant x-ray spectroscopic techniques. X-ray absorption spectroscopy (XAS) and resonant inelastic x-ray scattering (RIXS) spectra collected at the Cr $L_{2,3}$ edges reveal significant linear dichroism, which arises from the distorted octahedral environment surrounding the Cr$^{3+}$ ions. The origin of the bright excitons observed in this compound is examined through a comparison of the d-d excitations identified in the RIXS spectra, the x-ray excited optical luminescence (XEOL) spectra, and previously reported optical spectroscopic and theoretical studies. To further understand these phenomena, we develop a multiplet model based on a crystal electric field (CEF) approach that accounts for the local environment of Cr ions. This model successfully reproduces several experimental features, while also suggesting strong hybridization effects between Cr $3\textit{d}$ orbitals and ligands that are not fully captured by the present framework. These findings advance our understanding of the electronic structure and excitonic behavior in CrSBr and provide a foundation for future $\textit{in-situ}$ and $\textit{operando}$ studies of CrSBr-based devices for spintronic and optoelectronic applications.