Correlated Electron Effects in Chromium Trihalide Hetostructures with Graphene: A Tight-Binding Model Perspective

TL;DR

This paper develops a tight-binding model for CrX3 monolayers, revealing ligand-mediated electron pathways and analyzing charge transfer in graphene/CrX3 heterostructures, with implications for electronic and magnetic properties.

Contribution

It introduces a minimal tight-binding model for CrX3 monolayers that accurately captures conduction band features and ligand effects, and analyzes charge transfer in graphene/CrX3 heterostructures.

Findings

The model captures flat conduction bands requiring beyond nearest-neighbor hoppings.

Charge transfer occurs in graphene/CrX3 heterostructures, affecting electronic properties.

G/CrI3/G and G/CrI3 are type-II heterostructures with coexisting light holes and heavy electrons.

Abstract

In this study, we present an effective tight-binding model for an accurate description of the lowest energy quadruplet of conduction band in a ferromagnetic CrX$_3$ monolayer, tuned to the complementary \textit{ab initio} density functional theory simulations. This model, based on a minimum number of chromium orbitals, captures a distinctively flat dispersion in those bands but requires taking into account hoppings beyond nearest neighbours, revealing ligand-mediated electron pathways connecting remote chromium sites. Doping of states in the lowest conduction band of CrX$_3$ requires charge transfer, which, according to recent studies, can occur in graphene(G)/CrX$_3$ heterostructures. Here, we use the detailed description of the lowest conduction band in CrI$_3$ to show that G/CrI$_3$/G and G/CrI$_3$ are type-II heterostructures where light holes in graphene would coexist with heavy electrons in the magnetic layer, where the latter can be characterised by Wigner parameter $r_s\sim 15-20$ (as estimated for hBN-encapsulated structures).