Regensburg 2013 – scientific programme

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O: Fachverband Oberflächenphysik

O 55: Electronic Structure and Spin-Orbit Interaction II

O 55.11: Talk

Wednesday, March 13, 2013, 18:30–18:45, H42

Spin Polarized Photoemission from Bi2Te3 and Sb2Te3 Topological Insulator Thin Films — •Lukasz Plucinski^{1, 2}, Alexei Herdt^{1, 2}, Gustav Bihlmayer³, Gregor Mussler⁴, Sven Döring², Detlev Grützmacher⁴, Stefan Blügel³, and Claus M. Schneider^{1, 2} — ¹Peter Grünberg Institute PGI-6, Forschungszentrum Jülich, 52428 Jülich, Germany — ²Fakultät für Physik, Universität Duisburg-Essen, 47048 Duisburg, Germany — ³Peter Grünberg Institute PGI-1, Forschungszentrum Jülich, 52428 Jülich, Germany — ⁴Peter Grünberg Institute PGI-9, Forschungszentrum Jülich, 52428 Jülich, Germany

Spin polarized photoemission spectra from surfaces of Bi2Te3 and Sb2Te3 thin films show up to 45% in-plane spin polarization in the Dirac cone near the Fermi level, which is consistent with the dedicated ab initio theoretical results which find spin polarization in the order of 40-50% when averaged over the surface quintuple layer with the exponential depth profile related to the scattering mean free path of the VUV photoelectrons. Furthermore a non-zero out-of-plane spin polarization component is found in the Bi2Te3 hexagram Fermi surface.

We will discuss the spin-orbit entanglement mechanism behind the non-100% spin polarization in topologically protected surface states, and propose possible surface engineering solutions to increase the spin polarization of the Dirac cone in films grown by the MBE. Furthermore we will compare analytical band structure models with the DFT-based slab calculations.