Pure bulk spin photovoltaic effect in Altermagnets

The bulk photovoltaic effect (BPVE) generates a direct current (dc) under light in non-centrosymmetric systems, gaining attention for next-generation solar cells. The spin current counterpart, known as the "bulk spin photovoltaic effect", is also promising in spintronics. Studies show that light on antiferromagnets can generate pure spin currents, due to the cancellation of oppositely spin-polarized charge currents [1,2]. The ultra-fast response of BPVE makes it compatible with antiferromagnets, but generating pure spin currents requires mirror symmetries to separate spin and charge degrees of freedom, limiting material options.



We explore pure spin current generation via BPVE in altermagnets, which possess symmetries combining time-reversal and rotation operations that mimic mirror symmetries by acting differently on spin and charge currents. Our investigation of 27 non-centrosymmetric spin point groups shows that 17 can generate pure spin current. In altermagnetic Weyl semimetals, we also observe the quantization of the pure spin circular photogalvanic effect. These findings open new paths for spintronics and material research.



[1] Young et al., PRL 110, 057201 (2013)

[2] Fei et al., PRL 127, 207402 (2021)