Electronic properties of phases in the quasi-binary Bi2Se3-Bi2S3 system

We explored the properties of the quasi-binary BiSe-BiSsystem over a wide compositional range. X-ray diffraction analysis demonstrates that rhombohedral crystals can be synthesized within the solid solution interval 0-22 mol% BiS, while at 33 mol% BiSonly orthorhombic crystals are obtained. Core level photoemission spectroscopy reveals the presence of Bi, Seand Sspecies and the absence of metallic species, thus indicating that S incorporation into BiSeproceeds prevalently through the substitution of Se with S. Spin- and angle-resolved photoemission spectroscopy shows that topological surface states develop on the surfaces of the BiSeS(y<=0.66) rhombohedral crystals, in close analogy with the prototypical case of BiSe, while the orthorhombic crystals with higher S content turn out to be trivial semiconductors. Our results connect unambiguously the phase diagram and electronic properties of the BiSe-BiSsystem.