[seminar] SEMINAR na IF-u u CETVRTAK, 04. 11. 2010.

[Berislav Horvatic]

      Institut za fiziku, Bijenička cesta 46,

      predavaonica u zgradi Mladen Paić

      četvrtak, 4. studenog 2010, u 15:00 sati

       
     
      Graphene and Topological Insulators

       
     
      Dr. Carsten Busse
     
       

      II. Physikalisches Institut, Universität zu Köln,

      Zülpicher Str.77, 50937 Köln, Germany

       

      E-mail: busse at ph2.uni-koeln.de

       
     
      The scanning tunneling microscope (STM) is a powerful tool to study not only the geometric, but also the electronic structure of surfaces in atomic resolution. In this talk I will address the application of STM to two fascinating systems that have stimulated intense research in the last years, namely graphene and topological insulators.

      The new material graphene (Noble Prize in Physics 2010) currently receives an enormous attention for its exciting properties [1], caused by its monoatomic thickness and the unique band structure arising from its lattice symmetry. Here, we study the epitaxial growth of graphene on Ir(111), which leads to graphene of high structural quality which is only weakly bonded to the substrate [2-4]. Complementing STM, we determined key structural parameters using an x-ray standing wave (XSW) analysis. The results are corroborated by extensive DFT-calculations incorporating nonlocal interactions. Furthermore, graphene on Ir(111) is a template for the growth of metal cluster lattices (Ir, Pt, W, Re, Au, Fe) [5,6] showing a narrow size distribution and exceptional thermal stability.

      Topological insulators (TI) represent a new class of materials showing a bulk gap like an ordinary insulator but conducting states on their surface. These surface states are topologically protected against perturbations and impurity scattering by time-reversal invariance (TRI) [7]. Here, we study the Te-terminated (111) surface of Bi2Te3, a second generation 3D topological insulator. We investigated the surface state by analyzing interference patterns which are generated by electrons scattering at defects on the surface.




      [1]       A. K. Geim, Science 324, 1530 (2009).

      [2]       J. Coraux et al., Nano Lett. 8, 565, (2008).

      [3]        R. van Gastel et al., Appl. Phys. Lett. 95, 121901 (2009).

      [4]      I. Pletikosić et al., Phys. Rev. Lett., 102, 056808 (2009).

      [5]        A.T. N'Diaye et al., Phys. Rev. Lett., 97, 215501, (2006).

      [6]        A. T. N'Diaye et al., 11, 103045 (2009).

      [7]      M. Hasan C. Kane,  arXiv:1002.3895  (2010).



      http://www.ph2.uni-koeln.de/379.html
     
      Voditelji seminara IF-a:  Berislav Horvatić  &  Ivica Živković
     
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