The spin Hall effect (SHE), a key mechanism for generating spin currents, is typically uniform in bulk materials. In topological materials, however, the layer degree of freedom offers a novel avenue to control spin transport. Here, we demonstrate a layer-resolved SHE in the intrinsic antiferromagnetic topological insulator $\mathrm{Mn}{\mathrm{Bi}}_2{\mathrm{Te}}_4$. Using first-principles calculations and linear response theory, we reveal that the surface layers exhibit a spin Hall conductivity opposite in sign to that of the inner layers. This unusual layer selectivity stems from an abrupt change of the axion angle at the surface, which inverts the spin current direction while preserving the spin polarization alignment between the surface and subsurface layers with antiferromagnetic coupling. Our work establishes layer engineering as a powerful tool for manipulating spin currents and opens avenues for designing layer-resolved spintronic devices.

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• Spin Hall effect
• Spin current
• Topological materials
• Density functional calculations