Npj Comput. Mater.: 磁性贡献和晶格贡献势均力敌：二次谐波信号的最大调制

海归学者发起的公益学术平台

分享信息，整合资源

交流学术，偶尔风月

受此启发，来自中物院研究生院叶萌课题组、清华大学物理系徐勇/段文晖团队通过第一性原理计算和对称性分析研究了同时具有crystal SHG和MSHG的二维磁性材料，成功在其中揭示了一类巨大且可调控的NLMO效应。他们发现不同于以往实验研究的体材料，某些二维磁性材料，如三层CrI3和单层Cr2I3Br3，可在特定入射光频率处具有振幅相当的crystal SHG和MSHG，可以在磁矩翻转下产生最大化的干涉效应，使线偏振SHG偏振面旋转90°，打开或关闭圆偏振SHG光强，同时在固定磁构型时可以选择性导通某种手性的圆偏振光——即100%的SHG圆二色性。这些效应在单层材料中可以实现磁场调控的线偏振光偏振转换器、圆偏振光光开关和滤波器，在多层材料中还可以用于区分精细的磁构型。此外，作者还推导出了实现这些效应所需的SHG振幅和相位条件，并提出了利用二维材料的高度可调控性，通过调节层间距、自选轨道耦合强度、堆垛工程等方法来调控crystal SHG和MSHG的绝对和相对大小，达到两者振幅相当，从而广泛地实现这类巨大的NLMO效应。最后，他们还通过CrBr3和多层VSe2验证了这些调控方法的有效性和可迁移性，证明了这些巨大的NLMO效应是可调控的。

这项研究丰富了对NLMO效应的理解，增强了其应用，并提供了新的方法来调控不同类型SHG大小，为二维磁性材料的应用提供了新的可能性。

Fig. 1 | Concept of NLMO effects.

Fig. 2 | Atomic structures and SHG of the representative 2D magnets.

Fig. 3 | NLMO effects in representative 2D magnets.

Giant and controllable nonlinear magneto-optical effects in two-dimensional magnets

Dezhao Wu,  Meng Ye, Haowei Chen, Yong Xu & Wenhui Duan 

The interplay of polarization and magnetism in materials with light can create rich nonlinear magneto-optical (NLMO) effects, and the recent discovery of two-dimensional (2D) van der Waals magnets provides remarkable control over NLMO effects due to their superb tunability. Here, based on first-principles calculations, we reported giant NLMO effects in CrI3-based 2D magnets, including a dramatic change of second-harmonics generation (SHG) polarization direction (90°) and intensity (on/off switch) under magnetization reversal and a 100% SHG circular dichroism effect. We further revealed that these effects could not only be used to design ultra-thin multifunctional optical devices but also to detect subtle magnetic orderings. Remarkably, we analytically derived conditions to achieve giant NLMO effects and proposed general strategies to realize them in 2D magnets. Our work not only uncovers a series of intriguing NLMO phenomena but also paves the way for both fundamental research and device applications of ultra-thin NLMO materials.