Zhou Hang, Xiao Rui-Chun, Zhang Shu-Hui, Gan Wei, Han Hui, Zhao Hong-Miao, Lu Wenjian, Zhang Changjin, Sun Yuping, Li Hui, Shao Ding-Fu
Institute of Physical Science and Information Technology, <a href="https://ror.org/05th6yx34">Anhui University</a>, Hefei 230601, China.
Key Laboratory of Materials Physics, <a href="https://ror.org/04j3eks61">Institute of Solid State Physics</a>, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China.
Phys Rev Lett. 2024 Dec 6;133(23):236903. doi: 10.1103/PhysRevLett.133.236903.
Nonlinear optics plays important roles in the research of fundamental physics and the applications of high-performance optoelectronic devices. The bulk nonlinear optical responses arise from the uniform light absorption in noncentrosymmetric crystals, and hence are usually considered to be the collective phenomena of all atoms. Here we show, in contrast to this common expectation, the nonlinear optical responses in antiferromagnets can be selectively accumulated near the surfaces, representing a skin effect. This is because the inversion symmetry, despite being broken globally by magnetism, is barely violated locally deeply inside these antiferromagnets. Using A-type layered antiferromagnets as the representatives, we predict that the spatial-dependent nonlinear optical responses, such as the bulk photovoltaic effect and second harmonic generation, are notable in the top- and bottommost layers and decay rapidly when moving away from the surfaces. Such a phenomenon is strongly associated with the antiferromagnetism and exists in a broad range of antiferromagnets composed of centrosymmetric sublattices, offering promising device applications using these antiferromagnets. Our work uncovers a previously overlooked property of nonlinear optical responses and opens new opportunities for high-performance antiferromagnetic optospintronics.
非线性光学在基础物理研究和高性能光电器件应用中发挥着重要作用。块状材料的非线性光学响应源于非中心对称晶体中的均匀光吸收，因此通常被认为是所有原子的集体现象。然而，与这种普遍预期相反，我们发现反铁磁体中的非线性光学响应可以选择性地在表面附近累积，这表现为一种趋肤效应。这是因为尽管反演对称性在全局上被磁性打破，但在这些反铁磁体内部深处局部几乎未被破坏。以A型层状反铁磁体为代表，我们预测空间相关的非线性光学响应，如体光伏效应和二次谐波产生，在最顶层和最底层显著，而远离表面时则迅速衰减。这种现象与反铁磁性密切相关，并且存在于由中心对称子晶格组成的广泛反铁磁体中，为利用这些反铁磁体的器件应用提供了广阔前景。我们的工作揭示了非线性光学响应中一个此前被忽视的特性，并为高性能反铁磁光自旋电子学开辟了新机遇。
