Substrate induced electronic phase transitions of CrI[Formula: see text] based van der Waals heterostructures

Abstract

We perform first principle density functional theory calculations to predict the substrate induced electronic phase transitions of CrI[Formula: see text] based 2-D heterostructures. We adsorb graphene and MoS[Formula: see text] on novel 2-D ferromagnetic semiconductor-CrI[Formula: see text] and investigate the electronic and magnetic properties of these heterostructures with and without spin orbit coupling (SOC). We find that when strained MoS[Formula: see text] is adsorbed on CrI[Formula: see text], the spin dependent band gap which is a characteristic of CrI[Formula: see text], ceases to remain. The bandgap of the heterostructure reduces drastically ([Formula: see text] 70%) and the heterostructure shows an indirect, spin-independent bandgap of [Formula: see text] 0.5 eV. The heterostructure remains magnetic (with and without SOC) with the magnetic moment localized primarily on CrI[Formula: see text]. Adsorption of graphene on CrI[Formula: see text] induces an electronic phase transition of the subsequent heterostructure to a ferromagnetic metal in both the spin configurations with magnetic moment localized on CrI[Formula: see text]. The SOC induced interaction opens a bandgap of [Formula: see text] 30 meV in the Dirac cone of graphene, which allows us to visualize Chern insulating states without reducing van der Waals gap.

Figure 1

(a,b) The top and perspective view of the most stable configurations of 2:1 MoS${}_2$ on CrI${}_3$ respectively. The atom marked in red is the reference Mo atom with respect to which the various configurations have been named. (c,d) represent the same for 3:1 graphene on CrI${}_3$. The graphene ring with respect to which we fix the nomenclature is highlighted by the green atoms.

Figure 2

Spin-polarized projected density of states (DOS) and bandstructure for (a) pristine monolayer of $1\times 1$ CrI${}_3$ (b) pristine (unstrained) monolayer of $2\times 2$ MoS${}_2$ (c) 2:1 MS/CrI${}_3$ (Hollow configuration) with $2\times 2$ MoS${}_2$ adsorbed on $1\times 1$ CrI${}_3$. Gaussian smearing of 0.004 eV has been used to visualize the DOS.

Figure 3

The k-resolved DOS projected on individual atom types (KDOS(k,E)) refer to “Simulation methods” section for details) is shown for (a,b) The spin up and spin down bands for 2:1 MS/CrI${}_3$ projected on Mo states respectively. (c,d) The spin up and spin down bands projected on S respectively. (e,f) The spin up and spin down bands projected on Cr respectively. (g,h) The spin up and spin down bands projected on I respectively. The color scale has been normalized with respect to the maximum value of the state localized around their respective atom type.

Figure 4

Spin-polarized projected density of states (DOS) and bandstructure for (a) pristine monolayer CrI${}_3$ with $1\times 1$ unit cell (b) pristine monolayer graphene with $1\times 1$ unit cell (c) 3:1 G/CrI${}_3$ (top configuration) with $3\times 3$ graphene adsorbed on $1\times 1$ CrI${}_3$. Total DOS (grey) is magnified 2.5 times and DOS of C(dashed green) is magnified 5 times and Gaussian smearing of 0.004 eV has been used to visualize the DOS.

Figure 5

The k-resolved DOS projected on individual atom types (KDOS(k,E)) is shown for (a,b) The spin up and spin down bands for 3:1 G/CrI${}_3$ projected on Cr states respectively. (c,d) The spin up and spin down bands projected on I respectively. (e,f) The spin up and spin down bands projected on graphene respectively. The color scale has been normalized with respect to the maximum value of the state localized around their respective atom type.

Figure 6

Spin-orbit coupled (SOC) bandstructure of (a) 2:1 MS/CrI${}_3$ (b) 3:1 G/CrI${}_3$ heterostructures.