Dynamical correlations in single-layer CrI$_3$

TL;DR

This paper provides a first-principles study of the magnetic and spectral properties of monolayer CrI$_3$, revealing the importance of dynamical correlations in its electronic structure and optical behavior.

Contribution

It introduces a combined DFT and dynamical mean-field theory approach to accurately describe finite-temperature properties of monolayer CrI$_3$, highlighting differences from conventional DFT+$U$ methods.

Findings

Local moments form on Cr due to strong Coulomb interactions.

Electronic structure is modified by dynamical correlations, affecting orbital character.

Strong spin polarization of optical conductivity is predicted upon hole doping.

Abstract

Chromium triiodide is an intrinsically magnetic van der Waals material down to the single-layer limit. Here, we provide a first-principles description of finite-temperature magnetic and spectral properties of monolayer (ML) CrI$_3$ based on fully charge self-consistent density functional theory (DFT) combined with dynamical mean-field theory, revealing a formation of local moments on Cr from strong local Coulomb interactions. We show that the presence of local dynamical correlations leads to a modification of the electronic structure of ferromagnetically ordered CrI$_3$. In contrast to conventional DFT+$U$ calculations, we find that the top of the valence band in ML CrI$_3$ demonstrates essentially different orbital character for minority and majority spin states, which is closer to the standard DFT results. This leads to a strong spin polarization of the optical conductivity upon hole doping, which could be verified experimentally.