Berlin 2015 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 92: Topological Insulators I (jointly with MA, DS, HL, O)
TT 92.6: Talk
Thursday, March 19, 2015, 10:45–11:00, EB 202
Spin resolved momentum microscopy of the topological insulator Bi2Se3 — •Christian Tusche1, Martin Ellguth1, Shigemasa Suga1,2, Holger L. Meyerheim1, and Jürgen Kirschner1,3 — 1Max-Planck-Institut für Mikrostrukturphysik, Halle, Germany — 2Institute of Scientific and Industrial Research, Osaka, Japan — 3Institut für Physik, Martin-Luther-Universität, Halle, Germany
Topological insulators are a new class of materials that attracted wide interest by their electronic structure with unusual relations of electron spin and momentum, leading to highly spin polarized “Dirac-cone” surface states. Recently, comprehensive experimental access to such band structures became feasible by spin resolved momentum microscopy. This novel concept combines high resolution imaging of photoelectrons in two-dimensional (kx, ky) sections with a highly efficient imaging spin filter. Electron reflection at a Au/Ir(100) mirror allows us to measure 5000 spin-resolved points in the surface Brillouin zone, simultaneously.
We show that the band-structure of Bi2Se3 is characterized by highly spin polarized states within the complete Brillouin zone, beyond the “Dirac cone” surface state. For the latter we find that the spin polarization of photoelectrons can reach up to 90%, the highest value reported so far. A direct conclusion on the ground state polarization in these systems is complicated by the peculiar interplay between spin- and light-polarization in the photoemission, as directly observed in spin-resolved (kx, ky) images.
This work is supported by SPP1666 (Topological Insulators) of the DFG. M.E. acknowledges support by the BMBF (05K12EF1).