二维铁环体中自旋倾斜诱导的巨大非线性光学磁手性
Spin-canting-induced Giant Nonlinear Optical Magnetochirality in a 2D Ferrotoroid
AI总结：
该研究在二维铁环体双层CrSBr中，通过场诱导自旋倾斜打破PT对称性，利用i型与c型SHG极化率的相干干涉实现磁可切换圆偏振SHG信号，演示了磁光存储与逻辑操作，提供了二维自旋纹理的光学探针。
AI中文摘要：
实现磁可切换的手性光发射是二维光自旋电子学的重要目标。然而，传统策略在动态可调性和偏振对比度之间存在根本权衡。非线性光学，尤其是新兴的手性二次谐波产生（SHG）机制，提供了规避该限制的独特策略，但由于严格的对称性要求，其实验实现仍难以捉摸。在此，我们报道了中心对称二维铁环体双层（2L）CrSBr中的巨大非线性光学磁手性。我们发现，场诱导的自旋倾斜态打破了未受扰反铁磁（AFM）基态的宇称-时间（PT）对称性，激活了自旋手性驱动的i型极化率。这种涌现的i型与本征c型SHG极化率之间的相干干涉，产生了宏观圆偏振SHG信号，其螺旋度可通过磁场切换。利用这种敏感机制，我们发现了场饱和后逃避传统线性探针的剩磁态。通过利用这些态的非挥发性，我们演示了磁光存储和逻辑操作。我们的工作建立了一种通用的对称性驱动策略，用于定制非线性磁手性，同时为二维极限下的微妙自旋纹理提供了敏感的光学探针。
英文摘要：
Achieving magnetically switchable chiral light emission is an important goal for 2D opto-spintronics. However, conventional strategies face a fundamental trade-off between dynamic tunability and polarization contrast. Nonlinear optics, particularly the emerging mechanism of chiral second-harmonic generation (SHG), offers a distinct strategy to bypass this restriction, yet its experimental realization remains elusive due to stringent symmetry requirements. Here, we report giant nonlinear optical magnetochirality in a centrosymmetric 2D ferrotoroid, bilayer (2L) CrSBr. We reveal that a field-induced spin-canting state breaks the parity-time (PT) symmetry of the unperturbed antiferromagnetic (AFM) ground state, activating a spin-chirality-driven i-type susceptibility. The coherent interference between this emergent i-type and intrinsic c-type SHG susceptibilities generates a macroscopic circularly polarized SHG signal whose helicity is magnetically switchable. Leveraging this sensitive mechanism, we uncover remanent magnetic states after field saturation that evade conventional linear probes. By exploiting the non-volatility of these states, we demonstrate magneto-optical memory and logic operations. Our work establishes a general symmetry-driven strategy for tailoring nonlinear magnetochirality, while providing a sensitive optical probe for subtle spin textures in the 2D limit.
