X-ray spectra in magnetic van der Waals materials Fe$_3$GeTe$_2$, CrI$_3$, and CrGeTe$_3$: a first-principles study

TL;DR

This study uses first-principles DFT calculations to analyze X-ray spectra of magnetic van der Waals materials, assessing the accuracy of DFT+U methods and identifying optimal parameters for electronic structure description.

Contribution

It provides a detailed first-principles analysis of X-ray spectra in Fe$_3$GeTe$_2$, CrI$_3$, and CrGeTe$_3$, evaluating DFT+U's effectiveness and establishing optimal parameters.

Findings

DFT+U methods can reliably reproduce experimental spectra

Optimal U and J parameters are identified for each material

The relation between density of states and spectra is clarified

Abstract

Using density functional theory (DFT) methods, we have calculated X-ray absorption spectroscopy (XAS) and X-ray circular dichroism (XMCD) spectra in bulk and thin films of Fe$_3$GeTe$_2$, CrI$_3$, and CrGeTe$_3$. DFT+$U$ methods are employed for better handling of correlation effects of 3$d$ electrons of transition metals. We discuss relations between the density of states, radial matrix elements, and the corresponding spectra. By comparing the calculated spectra with previously measured spectra, we discuss the reliability of DFT+$U$ methods to describe the electronic structures of these materials and determine the corresponding optimal $U$ and $J$ parameters.