Doping induced evolution of Fermi surface in low carrier superconductor Tl-doped PbTe.

We have performed high-resolution angle-resolved photoemission spectroscopy on Tl-doped PbTe. We observed a distinct energy shift of the valence band and core levels upon Tl doping, together with the evolution of a small hole pocket around the X[over] point in the Brillouin zone, while no clear evidence for the localized states near the Fermi level is observed. These experimental results suggest that direct hole doping into the valence band and resultant emergence of a small Fermi surface are responsible for the metallic conductivity in Tl-doped PbTe.