PT-symmetry enabled spin circular photogalvanic effect in antiferromagnetic insulators

Abstract: The short timescale spin dynamics in antiferromagnets is an attractive feature from the standpoint of ultrafast spintronics. Yet generating highly polarized spin currents at room temperature remains a fundamental challenge for antiferromagnets. We propose a spin circular photogalvanic effect (spin-CPGE), in which circularly polarized light can produce a spin current without net charge current at room temperature, through an "injection-current-like" mechanism in parity-time(PT)-symmetric antiferromagnetic (AFM) insulators. We demonstrate this effect by first-principles simulations of bilayer CrI3 and room-temperature AFM hematite. Our calculations show that the spin-CPGE is significant, and the magnitude of spin photo-current is comparable with the widely observed charge photocurrent in ferroelectric materials. Interestingly, this spin photocurrent is not sensitive to spin-orbit interactions, which were regarded as fundamental mechanisms for generating spin current. Given the fast response of light-matter interactions, large energy scale, and insensitivity to spin-orbit interactions, our work gives hope to realizing a fast-dynamic and temperature-robust pure spin current in a wide range of PT-symmetric AFM materials, including weak-relativistic magnetic insulators and topological axion insulators.