Orbital Hall physics in two-dimensional Dirac materials

TL;DR

This paper explores how the orbital Hall effect manifests in two-dimensional Dirac materials, analyzing the influence of topology, energy gap, and disorder on orbital transport, revealing robustness of intra-atomic currents and minimal topological impact.

Contribution

It provides a detailed analysis of orbital Hall transport in 2D Dirac materials, highlighting the roles of topology, energy gap, and disorder, and distinguishes between intra-atomic and inter-atomic orbital currents.

Findings

Orbital Hall conductivity is influenced mainly by energy dispersion, not topology.

Intra-atomic orbital Hall current is more robust against disorder than inter-atomic.

Topology has little qualitative effect on orbital Hall conductivity.

Abstract

Orbitronics has recently emerged as a very active research topic after several proposals aiming to exploit the orbital degree of freedom for charge-free electronics. In this communication, we investigate orbital transport in selected two-dimensional systems to better understand which parameters govern the intra-atomic and inter-atomic contributions to the orbital Hall effect. We study the impact of the gap, the role of the materials' topology and the influence of the disorder on spin and orbital Hall transport. Starting from the Kane-Mele model, we describe how the orbital moment behaves depending on the material's topology and clarify the influence of the gap on the orbital Hall conductivity. We then extend the study to realistic topologically trivial and non-trivial materials, and find that the topology has little qualitative influence on the orbital Hall conductivity. In contrast, we observe that the energy dispersion has a more dramatic impact, especially in the presence of disorder. Remarkably, our results suggest that the intra-atomic orbital Hall current is more robust against scattering than the inter-atomic one, without further impact of the topological properties of the system under consideration.