We study the electronic structure of single crystal 1T-TiSe2 using temperature (T)-dependent soft x-ray photoemission spectroscopy (PES) and natural circular dichroism (NCD) across the charge-density-wave (CDW) transition at Tcdw∼200 K. We investigate detailed changes in energy positions and widths of the Ti 2p and Se 3d core-level spectra across Tcdw. The Ti 2p-3d-resonant PES shows a clear Ti 3d character two-hole correlation satellite in the valence band. A Cini-Sawatzky analysis indicates an effective attractive two-hole Coulomb interaction energy Udd =-1.3 eV. This attractive Coulomb energy is significantly larger than the known energy scale of excitonic correlations (< 100 meV) in 1T-TiSe2. On-resonant T-dependent measurements indicate that the strongly hybridized Ti 3d-Se 4p bands show increased hybridization in the CDW phase. On-resonant valence band spectra show a finite, possibly experimental geometry-related NCD of the states at and near the Fermi level which do not show T dependence across Tcdw. Given the presence of excitonic effects and the periodic lattice distortion, our results suggest that theoretical models need to take into account the attractive Coulomb interaction and hybridization changes for a complete understanding of the CDW in 1T-TiSe2.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics