Electronic Structure of the Topological Insulator Bi2Se3 Using Angle-Resolved Photoemission Spectroscopy: Evidence for a Nearly Full Surface Spin Polarization

We performed high-resolution spin- and angle-resolved photoemission spectroscopy studies of the electronic structure and the spin texture on the surface of Bi2Se3, a model TI. By tuning the photon energy, we found that the topological surface state is well separated from the bulk states in the vicinity of k(z) = Z plane of the bulk Brillouin zone. The spin- resolved measurements in that region indicate a very high degree of spin polarization of the surface state, similar to 0.75, much higher than previously reported. Our results demonstrate that the topological surface state on Bi2Se3 is highly spin polarized and that the dominant factors limiting the polarization are mainly extrinsic.