[Paper Review] Two-dimensional honeycomb-kagome V2O3: a robust room-temperature magnetic Chern insulator interfaced with graphene

Simon Mellaerts, Ruishen Meng+5 more|arXiv (Cornell University)|Jan 6, 2021

Topological Materials and Phenomena53 references25 citations

TL;DR

This study proposes a two-dimensional honeycomb-kagome V2O3 monolayer as a robust, room-temperature magnetic Chern insulator enabled by intrinsic spin-orbit coupling and strong electron correlations. First-principles calculations confirm its structural, thermal, and mechanical stability, with a predicted Curie temperature above 300 K and a quantized anomalous Hall effect, making it a promising candidate for spintronic devices when interfaced with graphene or under strain.

ABSTRACT

The possibility of dissipationless chiral edge states without the need of an external magnetic field in the quantum anomalous Hall effect (QAHE) offers a great potential in electronic/spintronic applications. The biggest hurdle for the realization of a room-temperature magnetic Chern insulator is to find a structurally stable material with a sufficiently large energy gap and Curie temperature that can be easily implemented in electronic devices. This work based on first-principle methods shows that a single atomic layer of V2O3 with honeycomb-kagome (HK) lattice is structurally stable with a spin-polarized Dirac cone which gives rise to a room-temperature QAHE by the existence of an atomic on-site spin-orbit coupling (SOC). Moreover, by a strain and substrate study, it was found that the quantum anomalous Hall system is robust against small deformations and can be supported by a graphene substrate.

Motivation & Objective

• To identify a structurally stable, two-dimensional magnetic Chern insulator with a large energy gap and Curie temperature suitable for room-temperature spintronic applications.
• To investigate the electronic and magnetic properties of a single-layer V2O3 with a honeycomb-kagome lattice structure.
• To evaluate the stability and feasibility of the system under biaxial strain and as a heterostructure on a graphene substrate.
• To determine the Curie temperature using quantum Monte Carlo and Green's function methods, assessing thermal robustness.
• To explore the role of on-site spin-orbit coupling and electron correlation (via DFT+U) in enabling the quantum anomalous Hall effect.

Proposed method

• Employed spin-polarized density functional theory (DFT) with the PBE-GGA functional and a Hubbard U correction (U = 3.28 eV) to account for localized 3d electrons in V2O3.
• Used the projected-augmented wave (PAW) method and a 550 eV plane-wave cutoff for electronic structure calculations.
• Applied the DFT-D3 method to include van der Waals interactions in the graphene-supported heterostructure.
• Performed ab initio molecular dynamics (AIMD) simulations at 300 K with a 4×4×1 supercell and 2 fs time steps to assess thermal stability.
• Calculated phonon dispersion via density functional perturbation theory (DFPT) to confirm dynamical stability.
• Estimated the Curie temperature using Monte Carlo simulations (VAMPiRE package) and a fully quantum-mechanical Green's function approach.

Experimental results

Research questions

• RQ1 Can a single-layer honeycomb-kagome V2O3 monolayer support a robust quantum anomalous Hall effect at room temperature?
• RQ2 How does the system respond to mechanical strain, and is it mechanically stable under biaxial deformation?
• RQ3 Can the magnetic Chern insulator state be stabilized when interfaced with a graphene substrate?
• RQ4 What is the role of spin-orbit coupling and electron correlation in generating the topological gap in this system?
• RQ5 What is the predicted Curie temperature, and does it exceed room temperature to enable practical applications?

Key findings

• The honeycomb-kagome V2O3 monolayer exhibits full structural, thermal, and mechanical stability, with no imaginary phonon modes and energy fluctuations below 0.3% in AIMD simulations.
• The system has a predicted Curie temperature of approximately 300 K, confirmed by both Monte Carlo and Green's function methods, indicating room-temperature ferromagnetism.
• A spin-polarized Dirac cone with a nontrivial Berry curvature leads to a quantized anomalous Hall conductance, confirming the quantum anomalous Hall effect.
• The system maintains its topological and magnetic properties under small biaxial strains (up to ±10%), demonstrating robustness against lattice distortions.
• The V2O3 monolayer can be stabilized on a graphene substrate with minimal interfacial interaction, preserving its magnetic and topological character.
• The effective Hubbard U parameter was self-consistently determined as 3.28 eV, consistent with bulk V2O3, validating the treatment of strong electron correlations.