Antiferromagnets (AFMs) recently demonstrate great potentials in efficient spin transport through magnons, providing a new platform for spintronics applications. Easy-plane AFMs, with two linearly polarized magnon eigenmodes that are orthogonal to each other, own unique advantages for low-energy control of ultrafast magnetic dynamics. However, it is commonly conceived that these magnon modes are less likely to transmit spins due to their vanishing angular momentum. In this talk, I will firstly discuss the progress and some remained questions in spin transmission through AFMs. I will present our recent experimental observation that an easy-plane insulating AFM, α-Fe2O3 thin film, can conduct efficient spin transmission over micrometer distance . Remarkably, the spin decay length shows an unconventional temperature dependence that cannot be captured by solely considering thermal magnon scatterings. These observations are interpreted by the interference of two linearly polarized propagating magnons, which is an analog to the birefringence effect in optics. Finally, our devices can realize a bi-stable spin-current switch with a 100% on/off ratio under zero remnant magnetic field, providing additional opportunities for nonvolatile, low-field control of spin transport in AFM systems.
 Han et al. Nature Nanotechnology 2020 (in press).