Unveiling Electronic Structure and Spin-Resolve of Bulk Bi<sub>2</sub>O<sub>2</sub>X (X = S, Se, and Te) Materials: A Computational Study Based-On Density Functional Theory

Bi 2 O 2 X (X = S, Se, and Te) group materials are widely studied compounds by replacing X atoms with group VI transition metals (chalcogens). We have systematically studied the electronic properties of the ternary compounds using the first-principle calculation density functional theory (DFT). We found that the Bi-p orbital dominantly characterized the conduction band minimum (CBM) located around the Gamma point, while the valence band maximum (VBM) located around the X point is mainly originated from the contribution of the chalcogen X-p orbitals. Focusing on the CBM at the Gamma point, we observed a fourfold-degenerate state at each band. Turning the SOC split these bands become double degenerate, except the Gamma point due to time reversibility. Further investigation of the spin component confirms that the double degenerate bands of Bi 2 O 2 X at the CBM around the Gamma point indicates the existence of the hidden spin polarization, which is a promising candidate for spintronics applications.