Optical control of spin splitting in a correlated altermagnet

Altermagnets are a new class of magnetic materials with zero net magnetization yet spin-split electronic bands in reciprocal space. The spin splitting arises from inequivalent crystal environments of the two spin sublattices. This combination is attractive for applications in spintronics and neuromorphic information technologies. Since the discovery of altermagnets, most research efforts have focused on identifying promising materials, whereas routes to tune the spin splitting remain largely unexplored. Optical tuning of exchange interactions in altermagnets offers a way to modify spin splitting on ultrafast timescales. Using real-time simulations of a two-dimensional multiband tight-binding (TB) model, we demonstrate that spin splitting in correlated altermagnets can be controlled on femtosecond timescales by optical excitation. The TB model includes local electronic correlations and strong coupling among charge, spin, orbital, and phonon degrees of freedom on equal footing. Our simulations reveal significant changes in the band structure and spin splitting of the altermagnet in response to optical excitation. Remarkably, the conduction-band spin splitting increases by up to a factor of four in the photoexcited state, and stronger light pulses further amplify the effect. By varying the Coulomb interaction U and Hund's exchange J, we disentangle their roles in enhancing the spin splitting after excitation. These findings show that optical excitation provides an effective approach to control spin splitting in altermagnets with correlated electrons.