Direct Observation of the Topological Surface States in Lead-Based   Ternary Telluride Pb(Bi1-xSbx)2Te4
  We have performed angle-resolved photoemission spectroscopy on Pb(Bi1-xSbx)2Te4, which is a member of lead-based ternary tellurides and has been theoretically proposed as a candidate for a new class of three-dimensional topological insulators (TIs). In PbBi2Te4, we found a topological surface state with a hexagonally deformed Dirac-cone band dispersion, indicating that this material is a strong TI with a single topological surface state at the Brillouin-zone center. Partial replacement of Bi with Sb causes a marked change in the Dirac carrier concentration, leading to the sign change of Dirac carriers from n-type to p-type. The Pb(Bi1-xSbx)2Te4 system with tunable Dirac carriers thus provides a new platform for investigating exotic topological phenomena. 
S. Souma, K. Eto, M. Nomura, K. Nakayama, T. Sato, T. Takahashi, Kouji   Segawa, and Yoichi Ando
cond-mat.mes-hall cond-mat.str-el