Modeling Terahertz Properties of Vanadium Dioxide by Ab Initio Computational Scheme and its Experimental Verification

A complete simulation scheme is established to model the terahertz (THz) properties of vanadium dioxide (VO₂) from ab initio to computational electromagnetic method. For the monoclinic insulating phase of VO₂, dielectric properties are computed by Hubbard-corrected density functional perturbation theory. Meanwhile, the electron-phonon interactions are studied to model the electronic transport properties of the tetragonal metallic phase of VO₂. In order to build a bridge from the microscopic effects of first-principles calculations to the macroscopic THz properties, the Drude model and effective medium theory are applied to model the dispersion properties of the material. To validate the proposed model, a VO₂ film grown on a sapphire substrate is fabricated and measured by a terahertz time-domain spectroscopy system. The measurement results have excellent agreements with the proposed simulations. Further, a VO₂-based THz metamaterial modulator is simulated by using the proposed model, in great agreement with the reported measurement result. Our ab initio computational scheme improves the simulation accuracy of design, which provides a solid THz modeling approach to the VO₂ and other insulator-metal transition metal oxides.