Dresden 2014 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 104: Topological Insulators (organized by MA)

TT 104.3: Talk

Friday, April 4, 2014, 10:00–10:15, HSZ 04

Combined STM/STS- and ARPES-investigation of the quaternary Topological Insulator Bi_1.5Sb_0.5Te_1.8Se_1.2 — •Thomas Bathon¹, Felix Reis¹, Christoph Seibel², Hendrik Bentmann², Paolo Sessi¹, Friedrich Reinert², and Matthias Bode¹ — ¹Physikalisches Institut, Experimentelle Physik II, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany — ²Physikalisches Institut, Experimentelle Physik VII, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany

We present a combined scanning tunneling microscopy/spectroscopy (STM/STS) and angular-resolved photoemission spectroscopy (ARPES) characterization of the electronic properties of the quaternary compound Bi_1.5Sb_0.5Te_1.8Se_1.2. ARPES-data evidence that this compound is still a Topological Insulator (TI) with a single Dirac cone, which is characteristic for the Bi₂X₃-class. The topological properties of the surface state, i.e. forbidden backscattering, have been confirmed by Fourier-transformed differential conductance (dI/dU) maps. Measurements performed both above and below the Fermi level allow us to determine the energy dispersion relation, the carrier velocity, and—by extrapolation to zero momentum—the position of the Dirac point. The observed scattering vectors are not as well-defined as those observed in binary compounds, probably due to substitutional disorder which results in a spatial fluctuation of the chemical potential. Our investigations illustrate how the properties of the well-known TI Bi₂Te₃ can be changed by chemical substitution.