  Spin photogalvanic effect (SPGE) is an efficient method to generate a spin
current by photoexcitation in a contactless and ultra-fast way. In
two-dimensional (2D) collinear antiferromagnetic (AFM) materials that preserve
the combined time-reversal (T) and inversion (I) symmetry (i.e., TI symmetry),
we find that the photogalvanic currents in two magnetic sublattices carry
different kinds of spins and propagate in opposite direction if the spin-orbit
coupling is negligible, resulting in a pure spin current without net charge
current. Based on the first-principles calculations, we show that two
experimentally synthesized 2D collinear AFM materials, monolayer MnPS$_3$ and
bilayer CrCl$_3$, host the required symmetry and support sizable SPGE. The
predicted SPGE in 2D collinear AFM materials makes them promising platforms for
nano spintronics devices.
