Electronic Structure Of A Thermoelectric Material: Bicuso

We investigate transport properties and the electronic structure of BiCuSO, a thermoelectric material which was predicted as a possible parent compound for unconventional superconductivity. For the p-type BiCuSO samples studied in this paper, our transport measurements show metallic behavior down to 2 K, and we observe an increase of saturated magnetic moment around 4 K, which could be due to the reorientation of the magnetic easy axis. Using angle-resolved photoemission spectroscopy measurements, we acquired the comprehensive electronic structure of BiCuSO including the predicted flat band, and by carrying out photon polarization dependent measurements we further investigated the orbital characters of bands near the Fermi level. Compared with its sister compound, BiCuSeO, we find the flat band could be the origin of high figure of merit (ZT) value in the BiCuChO (Ch = S, Se) family.