# Dresden 2014 – wissenschaftliches Programm

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# HL: Fachverband Halbleiterphysik

## HL 116: Topological insulators (organized by MA)

### HL 116.3: Vortrag

### Freitag, 4. April 2014, 10:00–10:15, HSZ 04

**Combined STM/STS- and ARPES-investigation of the quaternary Topological Insulator Bi**_{1.5}**Sb**_{0.5}**Te**_{1.8}**Se**_{1.2} — •Thomas Bathon^{1}, Felix Reis^{1}, Christoph Seibel^{2}, Hendrik Bentmann^{2}, Paolo Sessi^{1}, Friedrich Reinert^{2}, and Matthias Bode^{1} — ^{1}Physikalisches Institut, Experimentelle Physik II, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany — ^{2}Physikalisches 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_{1.5}Sb_{0.5}Te_{1.8}Se_{1.2}. ARPES-data evidence that this compound is still a Topological Insulator (TI) with a single Dirac cone, which is characteristic for the Bi_{2}X_{3}-class. The topological properties of the surface state, i.e. forbidden backscattering, have been confirmed by Fourier-transformed differential conductance (d*I*/d*U*) 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 Bi_{2}Te_{3} can be changed by chemical substitution.