Helical spin texture of Bi doped PbSb₂Te₄topological insulator

For the study of topological insulator (TI), scanning tunneling microscopy (STM) and angle-resolved photoemission spectroscopy (ARPES) are powerful tools to characterize the surface electronic properties. In the case of Bi₂Te₃ TI, a unique quasiparticle interference (QPI) pattern observed by STM revealed severe deformation of a Dirac cone. In search of the non-deformed ideal Dirac cone, Pb-based TIs were discovered. Pb-based TIs belong to peculiar topological class (1;111) whereas traditional TIs such as Bi₂Te₃ belong to (1;000). PbSb₂Te₄ is one of the Pb-based TIs, whose Fermi energy lies in the valence band. Therefore, its surface states are difficult to be observed by ARPES measurements.
In this study, we investigated the surface electronic properties of Bi doped PbSb₂Te₄ by STM. The helical spin texture of this compound is corroborated by a comparison between experimental and simulated QPI patterns. We also present the scattering process of carriers between the surface states.