Optically Tunable Spin Transport in Bilayer Altermagnetic Mott Insulators

Abstract: Altermagnets are a novel class of materials that combine antiferromagnetic spin ordering with non-relativistic spin splitting (NRSS) in their band structure, making them promising candidates for spintronics applications without requiring strong spin-orbit coupling. In this work, we investigate a two-dimensional bilayer Mott insulator that exhibits altermagnetic order. The interplay between spin and layer degrees of freedom gives rise to a complex symmetry-breaking pattern involving both magnetic and interlayer-coherent components. A key control parameter in the system is the layer polarization, which can be tuned via an external gate voltage. We show that applying an in-plane electric field with opposite signs in the two layers induces a polarization current that drives a spin current in each layer. While the polarization current is isotropic, the resulting spin current exhibits strong anisotropy and can be reversed by adjusting the photon energy. These findings suggest new avenues for manipulating spin transport in altermagnetic systems via electric and optical means.