Spin Caloritronics in Collinear Ferromagnetic Helical Structures under Irradiation

We study the charge and spin-dependent thermoelectric response of a ferromagnetic helical system irradiated by arbitrarily polarized light using a tight-binding framework and the Floquet–Bloch formalism. Transport properties for individual spin channels are determined by employing the nonequilibrium Green’s function technique, while phonon thermal conductance is evaluated using a mass-spring model with different lead materials. The findings reveal that light irradiation induces spin–split transmission features, suppresses thermal conductance, and yields favorable spin thermopower and figure of merit (FOM). The spin FOM consistently outperforms its charge counterpart under various light conditions. Moreover, long-range hopping is shown to enhance the spin thermoelectric performance, suggesting a promising strategy for efficient energy conversion in related ferromagnetic systems.