Spin current generation in an organic antiferromagnet via photo-excitation

We investigate the spin current generation in a one-dimensional organic antiferromagnetic system under light illumination via the quadratic response theory. We show that when the light energy is greater than the band gap of the system, a finite DC spin current of the shift type can be excited while the charge current remains zero. The spin conductivity is found to be an even function of the chemical potential μ, and can take comparatively large values around μ=0. The estimated nonlinear spin conductivity might be on the order of 10−6 ħe⋅A/V2, which is comparable to the values reported recently for some inorganic systems, indicating that the optical approach may be an efficient way to generate spin currents in organic materials.