Topological Magneto-Optical Effect and Its Quantization in Noncoplanar Antiferromagnets

Time: Thursday, October 25th, 11:00
Speaker: Wangxiang FENG, Beijing

Magneto-optical (MO) effects have been known for more than a century as they reflect the basic interactions between light and magnetism.  The origin of MO effects is normally believed by the simultaneous presence of band exchange splitting and spin-orbit coupling.  Using a tight-binding model and first-principles calculations, we show that topological MO effects, in analogy to the topological Hall effect, can arise in noncoplanar antiferromagnets caused entirely by scalar spin chirality instead of spin-orbit coupling.  The band exchange splitting is not indispensable to topological MO effects.  Moreover, the Kerr and Faraday rotation angles in two-dimensional or layered noncoplanar antiferromagnets are found to be quantized in the low-frequency limit, implying the appearance of quantum topological MO effects, which can be measured by time-domain THz spectroscopy.