Angle-resolved photoemission study of quasi one-dimensional TlInSe2

TlInSe2 with a quasi one-dimensional chain structure and a giant Seebeck coefficient of more than 106 μV/K below 140 °C has been investigated by means of angle-resolved photoemission spectroscopy at 50 K and 280 K. The obtained energy bands favorably agree with the calculated band structure and show quite noticeable dispersion in the direction normal to the chains. A rigid shift toward lower binding energies, a splitting and the formation of the mini-gap-like structures are clearly observed in the experimental electronic bands with the temperature reduced to 50 K. These features are indicative of an incommensurate superlattice phase emerging in TlInSe2 with temperature, and causing the record-breaking values of Seebeck coefficient.