Altermagnets have recently emerged as a new platform for spintronics applications, offering spin-split electronic bands despite vanishing net magnetization. Here, we investigate spin-current generation in Dirac altermagnets and identify Klein tunneling as an efficient mechanism for enhancing spin transport. Using a low-energy Dirac model combined with scattering theory, we demonstrate that Klein tunneling in altermagnets is strongly spin dependent and can be used to effectively control the electronic spin-current polarization by, for instance, adjusting the height, width, and orientation of the potential barrier. Finally, we explore how the $\ell$-wave symmetry of the Dirac altermagnet shapes the spin-current polarization and transmission, focusing especially on the $d$- and $g$-wave cases. Particularly promising results are obtained for the $g$-wave Dirac altermagnet, as it is found that the presence of a potential barrier can significantly boost the spin-current polarization, even when the intrinsic polarization due to the spin-split band structure is vanishingly small. For a barrier implemented via electrostatic gating, such a mechanism would, in turn, allow the spin-current polarization to be switched on and off via a gate voltage.

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• Dirac fermions
• Spintronics
• 2-dimensional systems
• Altermagnets
• Nanostructures