Regensburg 2013 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
O: Fachverband Oberflächenphysik
O 35: Poster Session I (Metal, semiconductor and oxide substrates: structure and adsorbates; Graphene)
O 35.69: Poster
Dienstag, 12. März 2013, 18:15–21:45, Poster B1
Can graphene be turned into a topological insulator? — •Carola Straßer1, Bart Ludbrook2, Andrea Damascelli2, Christian R. Ast1, and Klaus Kern1,3 — 1Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany — 2Quantum Matter Institute, UBC, Vancouver, BC V6T 1Z4, Canada — 3Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
In 2005 Kane and Mele [1] claimed that graphene opens a band gap at very low temperatures due to spin orbit coupling (SOC) and becomes a quantum spin Hall insulator. Since the SOC is very weak in carbon atoms the size of the gap is very small and experimentally not observable. Recently Weeks et al. [2] showed theoretically that the intrinsic SOC can be enhanced by depositing small amounts of heavy adatoms on top of a graphene sheet. The electrons which hop on the adatoms and back to the graphene sheet induce higher SOC. Calculations showed that this gives rise to a band gap of ΔSOC=25 meV at the K-point which should be observable with spectroscopic methods.
We performed angular resolved photoemission spectroscopy measurements at very low temperatures on epitaxial graphene on SiC. To induce higher SOC we decorated the sample with small amounts of Thallium. We observed small doping effects due to electron transfer from the adatoms to the graphene sheet. The doping level is increasing with coverage until it saturates. The band shift and indications for a gap opening will be presented in detail.
[1] C. L. Kane et al., Phys. Rev. Lett. 95, 226801 (2005)
[2] C. Weeks et al., Phys. Rev. X 1, 021001 (2011)