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Herdt A.,Jülich Research Center | Herdt A.,Center for Nanointegration Duisburg Essen | Plucinski L.,Jülich Research Center | Plucinski L.,Center for Nanointegration Duisburg Essen | And 15 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2013

The magnitude of electron spin polarization in topologically protected surface states is an important parameter with respect to spintronics applications. In order to analyze the warped spin texture in Bi 2Te3 thin films, we combine angle- and spin-resolved photoemission experiments with theoretical ab initio calculations. We find an in-plane spin polarization of up to ∼45% in the topologically protected Dirac cone states near the Fermi level. The Fermi surface of the Dirac cone state is warped and shows an out-of-plane spin polarization of ∼15%. These findings are in quantitative agreement with dedicated simulations which find electron density of the Dirac cone delocalized over the first quintuple layer with spin reversal occurring in the surface atomic layer. © 2013 American Physical Society.


Plucinski L.,Jülich Research Center | Plucinski L.,Fakultat For Physik And Center For Nanointegration Duisburg Essen Cenide | Plucinski L.,Julich Aachen Research Alliance Fundamentals of Future Information Technologies JARA FIT | Herdt A.,Jülich Research Center | And 21 more authors.
Journal of Applied Physics | Year: 2013

We have performed a combined spectroscopy and microscopy study on surfaces of Sb2Te3/Si(111) thin films exposed to air and annealed under ultra-high vacuum conditions. Scanning tunneling microscopy images, with atomic resolution present in most areas of such processed surfaces, show a significant amount of impurities and defects. Scanning tunneling spectroscopy reveals the bulk band gap of ∼ 170 meV centered ∼ 65 meV above the Fermi level. This intrinsic p-type doping behavior is confirmed by high-resolution angle-resolved photoemission spectra, which show the dispersions of the lower Dirac cone and the spectral weight of the bulk valence bands crossing the Fermi level. Spin-polarized photoemission revealed up to ∼15% in-plane spin polarization for photoelectrons related to the topologically protected Dirac cone states near the Fermi level, and up to ∼40% for several states at higher binding energies. The results are interpreted using ab initio electronic structure simulations and confirm the robustness of the time-reversal symmetry protected topological surface states in Sb2 Te3 in the presence of impurities and defects. © 2013 American Institute of Physics.


Ibach H.,Jülich Research Center | Ibach H.,Julich Aachen Research Alliance Fundamentals of Future Information Technologies JARA FIT | Rajeswari J.,Jülich Research Center | Rajeswari J.,Julich Aachen Research Alliance Fundamentals of Future Information Technologies JARA FIT | And 2 more authors.
Review of Scientific Instruments | Year: 2011

Based on 143° electrostatic deflectors we have realized a new spectrometer for electron energy loss spectroscopy which is particularly suitable for studies on surface spin waves and other low energy electronic energy losses. Contrary to previous designs high resolution is maintained even for diffuse inelastic scattering due to a specific management of the angular aberrations in combination with an angle aperture. The performance of the instrument is demonstrated with high resolution energy loss spectra of surface spin waves on a cobalt film deposited on the Cu(100) surface. © 2011 American Institute of Physics.

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