National Synchrotron Light Source Seminar

Layered dichalcogenides of Ti intercalated with transition metals TMxTiZ2 (TMDC's) where TM= Mn, Cr, Fe, Co, Cu or Ag and Z= S, Se, Te are low dimensional solids where monoatomic layers of TM atoms with a given density
are separated by nonmagnetic slabs of the TiZ2 matrix [1]. Discovery of charge-denstity wave (CDW) to superconductive state transition in Cu dichalcogenides and promise of that for Fe and Cr TMDC's inspired a number of studies of
their electronic structure [2] which are dedicated to understand the nature of superconductivity, the origin of magnetism and the formation of CDW.
The formation of electronic band structure and the chemical bonding situation were examined for three classes of compounds: TiZ2 host-lattice materials, TM
(Cr, Mn, Fe, Co) intercalates and Cr substitution compounds. Since electronic properties of TMDCs can be understood in terms of charge transfer and interlayer
separation [3], Soft X-ray Absorption, Soft X-ray Photoelectron and Soft X-ray Emission spectroscopies were used. It was found that a strong hybridization
between 3d orbitals of intercalated TM atom, Ti 3d and Z p orbitals plays a major role resulting in energy shifts of the conduction band, modications of the valence
band and variations of the density of states at the Fermi level [4]. The interplay between the band structure, interlayer separation and the chemical bonding of
TM atoms with a host lattice TiSe2 will be shown. Further opportunities for research of TMDCs and corresponding experimental challenges will be discussed.