Multifunctional Janus TiSBr monolayer: Strain-tuned synergy of ferrovalley, quantum anomalous Hall, and anomalous Nernst effects

Abstract

Two-dimensional ferrovalley materials that simultaneously exhibit large valley polarization and high Curie temperature (Tc) are essential for advancing valleytronic devices. In this work, we propose a stable Janus TiSBr monolayer as a ferromagnetic valley system with a Tc of 355 K. First-principles calculations show that out-of-plane magnetization induces a pronounced valley polarization of 68.94 meV, which together with valley-contrasting Berry curvature leads to the anomalous valley Hall effect (AVHE). Furthermore, biaxial strain provides effective control over its magnetic, valley, and topological properties. Remarkably, under a narrow compressive strain window between −3.89% and −4.0%, the system undergoes a transition from the AVHE to both the quantum anomalous Hall effect and the anomalous Nernst effect, revealing its multifunctional nature. These results establish the Janus TiSBr monolayer as a promising platform for integrated valleytronic, spintronic, and topological applications.