Berlin 2015 – scientific programme

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O: Fachverband Oberflächenphysik

O 69: Ultrafast Electron and Spin Dynamics

O 69.3: Poster

Wednesday, March 18, 2015, 18:15–21:00, Poster A

Spectroscopy and dynamics of unoccupied electronic statesof the topological insulators Sb₂Te₃ and Sb₂Te₂Se — •Johannes Reimann, Jens Güdde, Kenta Kuroda, and Ulrich Höfer — Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität, D-35032 Marburg

The electronic structure and ultrafast electron dynamics of the p-doped topological insulator Sb₂Te₃ and its derivative Sb₂Te₂Se was investigated by means of time- and angle-resolved two-photon photoemission (2PPE). Our experiment reveal that the massless Dirac-cone like energy dispersion of topological surface states is realized above the Fermi energy in both materials. In agreement with theoretical predictions we find that the unoccupied bands of Sb₂Te₂Se are shifted to higher energies as compared to Sb₂Te₃. The observed electron dynamics in the topological surface state (TSS) of both materials is, however, very similar, which is a signature that the decay is dominated by the number of unoccupied states in the valence band. At lower temperatures at which the electron mobility in the bulk is enhanced, the decay becomes surprisingly faster, which strongly indicates that transport perpendicular to the surface into the bulk conduction band is important for the decay of the TSS.