Pure spin current generation in two-dimensional (2D) altermagnets is of considerable interest in spintronics. Here, we develop a general phenomenological formalism for the spin Hall effect driven by the circular bulk photovoltaic effect (BPVE) in 2D semiconducting altermagnets with $C_{4\text{v}}$ and $D_{2\text{d}}$ symmetry. In such altermagnetic systems, the spin splitting in the momentum space is alternated between the $\mathrm{\Gamma }\to X$ and $\mathrm{\Gamma }\to Y$ directions, and the photoresponse tensor of the BPVE, ${\gamma }_{xy}$ and ${\gamma }_{yx}$ are equal in magnitude. This enables the generation of a pure spin current along the transverse direction, while a charge current along the longitudinal direction, thereby inducing the spin Hall effect via the circular BPVE. The spin Hall angle can be calculated from the spin-polarized photoresponse tensors. Specifically, we demonstrate through first-principles calculations and quantum transport simulations that a sizable spin Hall effect can be induced in the 2D altermagnet ${\mathrm{V}}_2\mathrm{SeTeO}$($C_{4\text{v}}$ symmetry), which exhibits a spin Hall angle much larger than 1, indicating high efficiency in pure spin current generation. Our results show the promise of altermagnets for spintronic applications.

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• Photocurrent
• Spin Hall effect
• 2-dimensional systems
• Altermagnets
• Density functional calculations