Spin orbit splitting in the valence bands of ZrSxSe2−x: Angle resolved photoemission and density functional theory

► We performed high resolution ARPES on 1T-ZrSxSe2−x. ► A characteristic splitting of the chalcogen p-derived VB along high symmetry directions was observed. ► The splitting size at the A point of the BZ is found to increase from 0.06 to 0.31 eV from ZrS2 towards ZrSe2. ► Electronic structure calculations based on the DFT were performed using the model of TB-MBJ. ► The calculations show that the splitting is due to SO coupling of the valence bands.