Band Structure of Topological Insulator BiSbTe1.25Se1.75

In this talk, I will present my angle resolved photoelectron spectroscopy (ARPES) and density functional theory results on quaternary topological insulator (TI) BiSbTe1.25Se1.75 (BSTS). This study confirms the non-trivial topology of the surface state bands (SSBs) in BSTS. The SSBs are sensitive to the atomic composition of the terminating surface and have a partial 3D character. Further study shows that the band bending (BB) effects in BSTS and the Dirac point (DP) shifts by more than two times compared to that in Bi2Se3 to reach the saturation. The stronger BB in BSTS could be due to the difference in screening of the surface charges. From momentum density curves (MDCs) of the ARPES data we obtained an energy dispersion relation showing the warping strength of the Fermi surface in BSTS to be intermediate between those found in Bi2Se3 and Bi2Te3 and also to be tunable by controlling the ratio of chalcogen/pnictogen atoms. In addition, experiments also reveal that the nature of the BB effects are highly sensitive to the exposure of the fresh surface to various gas species. These findings have important implications in the tuning of DP in TIs for technological applications.