Progress and challenges for two-dimensional spin-polarized quantum materials

The physical descriptions of known materials are based on quantum mechanics, which describes how atoms bond and electrons interact at a fundamental level. However, there is increasing interest in materials systems that maintain quantum effects across a wider range of energy and length scales. In recent years, the research and development boom of two-dimensional (2D) materials and quantum systems with spin polarization have attracted widespread attention. However, there is still a lack of summary and discussion regarding state-ofthe-art advances and challenges. This review focuses on the recent progress and challenges of 2D spinpolarized quantum materials (SQMs). First, two important intrinsic properties of 2D SQMs are presented: tunable electronic band structure and intrinsic magnetism. Second, some spin-polarization properties in 2D SQMs are discussed, involving spin polarization in 2D topological materials and topological spin textures. Third, several interesting quantum properties in 2D SQMs are summarized, including quantum Hall effect family, quantum properties in moire<acute accent> superlattices, and superconductivity. Fourth, two key spintronic devices based on 2D SQMs are introduced: magnetoresistance devices and electrical magnetization switching devices. Finally, some important opportunities and challenges of 2D SQMs are briefly addressed.