Designing light-element materials with large effective spin-orbit coupling

TL;DR

This paper presents a method to enhance spin-orbit coupling in light elements by leveraging crystal symmetry and electron correlation, leading to the prediction of new high-temperature quantum anomalous Hall insulators.

Contribution

It introduces design principles and a comprehensive database for identifying light-element materials with strong SOC effects, enabling the discovery of promising spintronic materials.

Findings

Identified mechanisms to amplify SOC in 3d and 4d systems.

Predicted nine 2D materials as high-temperature quantum anomalous Hall insulators.

Provided a database of crystal symmetries for SOC enhancement.

Abstract

Spin-orbit coupling (SOC), the core of numerous condensed-matter phenomena such as nontrivial band gap, magnetocrystalline anisotropy, etc, is generally considered to be appreciable only in heavy elements, detrimental to the synthetization and application of functional materials. Therefore, amplifying the SOC effect in light elements is of great importance. Here, focusing on 3d and 4d systems, we demonstrate that the interplay between crystal symmetry and electron correlation can dramatically enhance the SOC effect in certain partially occupied orbital multiplets, through the self-consistently reinforced orbital polarization as a pivot. We then provide design principles and comprehensive databases, in which we list all the Wyckoff positions and site symmetries, in all two-dimensional (2D) and three-dimensional crystals that potentially have such enhanced SOC effect. As an important demonstration, we predict nine material candidates from our selected 2D material pool as high-temperature quantum anomalous Hall insulators with large nontrivial band gaps of hundreds of meV. Our work provides an efficient and straightforward way to predict promising SOC-active materials, releasing the burden of requiring heavy elements for next-generation spin-orbitronic materials and devices.