Light-assisted Néel spin currents in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi mathvariant="script">PT</mml:mi></mml:math>-symmetric antiferromagnetic semiconductors

Abstract

N\'eel spin current is defined as the staggered spin current across different magnetic sublattices and can manipulate the N\'eel vector of the antiferromagnet by its associated spin-transfer torques. Currently, it is believed that N\'eel spin currents are only generated through electrical driving in $\mathcal{PT}$-symmetric antiferromagnetic metals, which is a linear effect. In this paper, we propose that N\'eel spin currents can be induced through the nonlinear optical effect (spin photogalvanic effect) in $\mathcal{PT}$-symmetric antiferromagnetic semiconductors. Using CrSBr and ${\mathrm{CrI}}_{3}$ as representatives, we predict that light can generate N\'eel spin current in antiferromagnetic semiconductors, with both staggered and antiparallel spin currents distributed across different magnetic sublattices, depending on the $\mathcal{PT}$ symmetries of their corresponding spin photogalvanic coefficients. We show that the origin of the diverse manifestations of light-assisted N\'eel spin currents lies in the nonlinearity of the spin photogalvanic effect, resulting in the current not necessarily being the staggered spin current. Our work proposes a nonlinear effect that may have tremendous application potential in future antiferromagnetic devices.