Emergence of a Chern-insulating state from a semi-Dirac dispersion

TL;DR

This paper demonstrates the emergence of a Chern-insulating state in a semi-Dirac system, specifically in TiO2/VO2 heterostructures, combining first-principles calculations and a new semi-Dirac model to reveal topological properties.

Contribution

It introduces a semi-Dirac model formed by merging three Dirac points and shows how nontrivial topology arises in semi-Dirac dispersions.

Findings

Chern number of -2 for valence bands

Existence of gapless chiral edge states

Quantized Hall conductivity of 2e^2/h

Abstract

A Chern insulator (quantum anomalous Hall insulator) phase is demonstrated to exist in a typical semi-Dirac system, the TiO2/VO2 heterostructure. By combining first-principles calculations with Wannier-based tight-binding model, we calculate the Berry curvature distribution, finding a Chern number of -2 for the valence bands, and demonstrate the existence of gapless chiral edge states, ensuring quantization of the Hall conductivity to 2e^2/h. A new semi-Dirac model, where each semi-Dirac cone is formed by merging three conventional Dirac points, is proposed to reveal how the nontrivial topology with finite Chern number is compatible with a semi-Dirac electronic spectrum.