We show that large magneto-optic Kerr effects (MOKEs) emerge when an antiferromagnet (AFM) is proximately coupled to a topological insulator (TI) film—where neither the perfect collinear Néel ordered single-domain AFM nor the unmagnetized TI individually shows any MOKE. Because of the lack of macroscopic magnetization, the AFM only couples to the spin of one of the TI’s surfaces breaking time-reversal and inversion symmetry—which leads to a small microdegree MOKE signal. This small MOKE can be easily enhanced by 5 orders of magnitude, via cavity resonance, by optimizing the AFM and TI film thicknesses on the substrate. For slightly off-resonant structures, a $6^{\circ }$ Kerr rotation can be electrically switched on by varying the Fermi energy. This requires less than 20 meV, which is encouraging for low-power spintronics and magneto-optic devices. We further show that this simple structure is easily resilient to 5% material growth error.

中文翻译：

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反铁磁体-拓扑绝缘体异质结构中的异常磁光效应

我们表明，当反铁磁体 (AFM) 与拓扑绝缘体 (TI) 膜紧密耦合时，会出现大型磁光克尔效应 (MOKE)——其中完美共线的 Néel 有序单域 AFM 和未磁化的 TI 均未单独显示任何 MOKE . 由于缺乏宏观磁化，AFM 仅与 TI 表面之一的自旋耦合，从而破坏了时间反转和反转对称性——这会导致微小的 MOKE 信号。通过优化基板上的 AFM 和 TI 薄膜厚度，这种小型 MOKE 可以通过腔谐振轻松增强 5 个数量级。对于稍微偏共振的结构，a$6^{\circ }$克尔旋转可以通过改变费米能量来电开启。这需要不到 20 meV，这对于低功率自旋电子学和磁光器件来说是令人鼓舞的。我们进一步表明，这种简单的结构很容易适应 5% 的材料生长误差。