Unconventional strong 3p–3d orbital hybridization in sulfur-doped FeSe: for tailored ultrathin electromagnetic wave absorbers

Anion doping engineering is an effective method to regulate the electronic structure of transition metal dichalcogenides (TMDs), especially at the electron orbital level. Based on electromagnetic wave (EMW) loss theory, this study innovatively constructs dipole polarization sites <i>via</i> S doping in FeSe. The electronic structure of these sites is systematically analyzed to reveal charge redistribution and bond hybridization induced by dopant incorporation. Notably, controlled sulfur doping induces Fe-to-S charge transfer, enhances interatomic electron transfer, and forms numerous dipolar polarization centers, enabling precise tuning of EM parameters. Density of states and wave function calculations reveal strong Fe 3d-S 3p orbital hybridization, intensifying local charge imbalances and dipole polarization. S doping also modulates the bandgap, suppresses free electron concentration, and improves impedance matching. Compared with Pure FeSe, the effective absorption bandwidth (EAB) of FeSe_1-<i>x</i>S_<i>x</i> reaches 5.52 GHz at a thickness of only 1.3 mm, an increase of 132.5%. The minimum reflection loss (RL) is -59.6 dB, an improvement of 196.5%. This work provides a theoretical foundation for constructing polarization centers.