Spinning Radiation from Topological Insulator

Axion coupling in topological insulator (TI) gives rise to unusual electromagnetic phenomena such as induction of image magnetic monopole, Faraday rotation etc. Here we show this coupling also leads to emergence of spin angular momentum (SAM) in the thermal radiation from TI (Phys. Rev. B 100, 081408(R)). A slab of TI with a thin magnetic coating would radiate light with the same degree of circular polarization in all directions, in contrast to conventional thermal emitters with structured interface. Through the control of emission of SAM, TIs may, therefore, find potential applications in generation of structured light from thermal sources.