Electronic structures of the metal-to-insulator transition system 1T-TaSxSe2-x studied by angle-resolved photoemission spectroscopy

We have investigated the electronic structures of metal-to-insulator transitions (MIT) due to charge-density-wave phase transition in 1T-TaSxSe2-x by angle-resolved photoemission spectroscopy. In the insulating phase of the sample with x = 1.5, we observe a gap formation at the Fermi energy (E-F), while in the metallic phase of the sample with x = 1.2, we do not observe a drastic change in the spectra between at room temperature and at low temperature. We observe a peak originating from the lower Hubbard band in the insulating phase of the sample with x = 1.5. In the metallic phase of the sample with x = 1.2, the peak intensity is smaller and the peak energy shifts near E-F, but the lower Hubbard band peak still remains. These results suggest that MIT in 1T-TaSxSe2-x is due to the Mott localization.