Electronic structure and excitonic optical response of iron telluride (FeTe) from first-principles calculations

First-principles calculations were performed to study the electronic structure and interband optical response of FeTe using density functional theory within the Vienna Ab initio Simulation Package, with post-processing carried out using VASPKIT. The calculated band structure identifies FeTe as a spin-polarized multiband metal, with low-energy states near the Fermi level dominated by Fe-3d orbitals and moderate Fe-Te hybridization away from it. The interband dielectric response was analyzed within the independent-particle approximation (IPA), the random-phase approximation (RPA), and the Bethe-Salpeter equation (BSE). Beyond IPA, the spectra mainly show a redistribution of interband oscillator strength. In the low-energy region, the calculated spectra are therefore discussed primarily in terms of interband features, while noting that additional intraband contributions may also be relevant for a full description of the metallic response. These results provide a compact first-principles description of the electronic structure and interband optical properties of FeTe.