Splitting of the Ti-3d bands of TiSe₂ in the charge-density wave phase

Highlights: • Angle resolved photoemission spectroscopy (ARPES). • Charge density wave (CDW). • TiSe₂- Splitting of the conduction bands. Horizontal and vertical polarizations. Temperature dependence. - Abstract: Very high resolution angular resolved photoemission (ARPES) spectra on TiSe₂ in two distinct polarization geometries (vertical and horizontal) at temperatures between 300 K and 22 K enabled the observation of details of bands near the Fermi level not reported so far. Calculations of the electronic band structure based on density functional theory (DFT) using B3LYP hybrid functional and MBJ potential (with and without spin-orbit coupling) were performed to obtain the orbital symmetry and dispersion. Two degenerate conduction bands (CB's) were observed at the Γ-point, a weak CB- emission at the A-point, and two non degenerate CB's (i.e. splitting of CB) at the M/L-point of the Brillouin Zone (BZ). The splitting was detected at L for both polarizations, while at M remarkably only for horizontal polarization. These results cannot be fully accounted for by current theories for the charge density wave (CDW) and point to a reduced symmetry of the electronic states, possibly due to the chiral CDW.