Berlin 2015 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 67: Topological insulators I (MA with HL/TT)

HL 67.6: 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 Suga^1,2, Holger L. Meyerheim¹, and Jürgen Kirschner^1,3 — 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 (k_x, k_y) 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 (k_x, k_y) images.

This work is supported by SPP1666 (Topological Insulators) of the DFG. M.E. acknowledges support by the BMBF (05K12EF1).