Recent advances in two-dimensional low-symmetry materials: Crystal structures, modulation strategies, and functional applications

Two-dimensional (2D) low-symmetry materials have shown unique advantages in polarization photonic devices and neuromorphic computing due to their inherent in-plane anisotropy. This article systematically summarizes the research progress of 2D low-symmetry materials from 2020 to 2025. Firstly, these materials are classified according to their crystal symmetry (orthorhombic, monoclinic, and triclinic systems), and their structural features, as well as the anisotropic optical, electrical, and optoelectronic properties, are elaborated in detail. Then, four methods, including strain engineering, external field modulation, crystal structure engineering, and interface symmetry engineering, are used to analyze the anisotropy enhancement strategies and their potential mechanisms. Subsequently, the applications of these materials, including polarization detection imaging and neuromorphic devices, are discussed. Finally, we offer insights based on the possible challenges and development trends of current low-symmetry materials. We expect to provide a comprehensive reference for the fundamental research and device applications of 2D low-symmetry materials.