Toyoda Shingo, Fiebig Manfred, Arima Taka-Hisa, Tokura Yoshinori, Ogawa Naoki
RIKEN Center for Emergent Matter Science (CEMS), Saitama 351-0198, Japan.
Department of Materials, ETH Zurich, 8093 Zurich, Switzerland.
Sci Adv. 2021 Apr 16;7(16). doi: 10.1126/sciadv.abe2793. Print 2021 Apr.
Mirror symmetries are of particular importance because they are connected to fundamental properties and conservation laws. Spatial inversion and time reversal are typically associated to charge and spin phenomena, respectively. When both are broken, magnetoelectric cross-coupling can arise. In the optical regime, a difference between forward and backward propagation of light may result. Usually, this nonreciprocal response is small. We show that a giant nonreciprocal optical response can occur when transferring from linear to nonlinear optics, specifically second harmonic generation (SHG). CuBO exhibits SHG transmission changes by almost 100% upon reversal of a magnetic field of just ±10 mT. The observed nonreciprocity results from an interference between magnetic-dipole and electric-dipole SHG. Although the former is inherently weaker than the latter, a resonantly enhanced magnetic-dipole transition has a comparable amplitude as a nonresonant electric-dipole transition, thus maximizing the nonreciprocity. Multiferroics and magnetoelectrics are an obvious materials platform to exhibit nonreciprocal nonlinear optical functionalities.
镜面对称尤为重要，因为它们与基本性质和守恒定律相关联。空间反演和时间反演通常分别与电荷和自旋现象相关。当两者都被打破时，可能会出现磁电交叉耦合。在光学领域，光的正向和反向传播之间可能会产生差异。通常，这种非互易响应很小。我们表明，当从线性光学转换到非线性光学，特别是二次谐波产生（SHG）时，可能会出现巨大的非互易光学响应。在仅±10 mT的磁场反转时，CuBO的SHG传输变化几乎达到100%。观察到的非互易性源于磁偶极子和电偶极子SHG之间的干涉。尽管前者本质上比后者弱，但共振增强的磁偶极子跃迁具有与非共振电偶极子跃迁相当的幅度，从而使非互易性最大化。多铁性材料和磁电材料是展现非互易非线性光学功能的明显材料平台。
