Topology-Engineered Orbital Hall Effect in Two-Dimensional Ferromagnets

Abstract

Recent advances in the manipulation of the orbital angular momentum (OAM) within the paradigm of orbitronics presents a promising avenue for the design of future electronic devices. In this context, the recently observed orbital Hall effect (OHE) occupies a special place. Here, focusing on both the second-order topological and quantum anomalous Hall insulators in two-dimensional ferromagnets, we demonstrate that topological phase transitions present an efficient and straightforward way to engineer the OHE, where the OAM distribution can be controlled by the nature of the band inversion. Using first-principles calculations, we identify Janus RuBrCl and three septuple layers of MnBi 2 Te 4 as experimentally feasible examples of the proposed mechanism of OHE engineering by topology. With our work, we open up new possibilities for innovative applications in topological spintronics and orbitronics.

Design of Antiferromagnetic Second-Order Band Topology with Rotation Topological Invariants in Two Dimensions

“…For an n th-order topological insulator (TI) in d spatial dimensions, protected in-gap states are featured at its d – n dimensional boundary with 1 < n ≤ d . Among various HOTIs, two-dimensional (2D) second-order topological insulators (SOTIs) that possess a gapped bulk and no gapless edge states have attracted enormous research interest. − A 2D SOTI manifests topologically protected 0-dimensional (0D) corner states, which are usually depicted by fractionally quantized corner charge whose quantization is symmetry protected and can change in discrete jumps at topological phase transitions. − Currently, although the 2D SOTI phase has been proposed for a long time, almost all of the experimental observations have only been verified in artificial crystal systems, such as photonic systems, − acoustic systems, − and electric circuits. − Despite being the most crucial frontier of topological matter, 2D SOTI phases in electronic materials have not yet been found in experiments, posing a great obstacle for further studies on higher-order topological physics and related application research.…”