Valence band electronic structure of the van der Waals ferromagnetic insulators: VI$_3$ and CrI$_3$

TL;DR

This study uses ARPES to detail the electronic structures of vdW ferromagnetic insulators CrI3 and VI3, revealing a 1 eV band gap and differences in valence band composition, challenging some theoretical models.

Contribution

It provides the first detailed ARPES measurements of CrI3 and VI3, clarifying their electronic structures and highlighting discrepancies with existing theoretical predictions.

Findings

Band gap of approximately 1 eV observed

Contradicts some theoretical models predicting Dirac half-metallicity

Distinct valence band compositions for CrI3 and VI3

Abstract

Ferromagnetic van der Waals (vdW) insulators are of great scientific interest for their promising applications in spintronics. It has been indicated that in the two materials within this class, CrI$_3$ and VI$_3$, the magnetic ground state, the band gap, and the Fermi level could be manipulated by varying the layer thickness, strain or doping. To understand how these factors impact the properties, a detailed understanding of the electronic structure would be required. However, the experimental studies of the electronic structure of these materials are still very sparse. Here, we present the detailed electronic structure of CrI$_3$ and VI$_3$ measured by angle-resolved photoemission spectroscopy (ARPES). Our results show a band-gap of the order of 1 eV, sharply contrasting some theoretical predictions such as Dirac half-metallicity and metallic phases, indicating that the intra-atomic interaction parameter (U) and spin-orbit coupling (SOC) were not properly accounted for in the calculations. We also find significant differences in the electronic properties of these two materials, in spite of similarities in their crystal structure. In CrI$_3$, the valence band maximum is dominated by the I 5{\it p}, whereas in VI$_3$ it is dominated by the V 3{\it d} derived states. Our results represent valuable input for further improvements in the theoretical modeling of these systems.