First-principles and tight-binding analysis of thermoelectricity in irradiated WSe$_2$
Electronic and thermoelectric transport in zigzag monolayer WSe$_2$ nanoribbons are studied under monochromatic irradiation. The electronic structure is described within a six-orbital tight-binding framework constructed from the relevant tungsten and selenium orbitals, with atomic spin-orbit coupling included explicitly. Periodic driving is incorporated via the Peierls substitution, and in the high-frequency limit the system is mapped onto an effective static Floquet Hamiltonian with polarization-dependent renormalized hoppings. Coherent transport is evaluated using wave-function matching within the Landauer-Büttiker formalism. The lattice thermal conductivity is obtained independently from density functional perturbation theory combined with an iterative solution of the phonon Boltzmann transport equation. Light-induced hopping renormalization reshapes the band dispersion and transmission spectrum near the Fermi level, modifying the Landauer transport integrals that determine electrical and thermal conductances and the Seebeck coefficient. Together with spin-orbit-driven band splitting and reduced lattice thermal conductivity from enhanced anharmonic scattering, this leads to a thermoelectric figure of merit $ZT$ exceeding unity over a broad temperature range.