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Contrast Reversal in Scanning Tunneling Microscopy and Its Implications for the Topological Classification of SmB6 |
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| Authors: | Hannes Herrmann Peter Hlawenka Konrad Siemensmeyer Eugen Weschke Jaime Sánchez-Barriga Andrei Varykhalov Natalya Y. Shitsevalova Anatoliy V. Dukhnenko Volodymyr B. Filipov Slavomir Gabáni Karol Flachbart Oliver Rader Martin Sterrer Emile D. L. Rienks |
| Affiliation: | 1. Institut für Physik, Karl-Franzens-Universität Graz, Universitätsplatz 5, 8010 Graz, Austria;2. Helmholtz-Zentrum Berlin für Materialien und Energie, Elektronenspeicherring BESSY II, Albert-Einstein-Straße 15, 12489 Berlin, Germany;3. Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, Krzhyzhanovsky str. 3, 03142 Kiev, Ukraine;4. Institute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, 04001 Košice, Slovakia |
| Abstract: | SmB6 has recently attracted considerable interest as a candidate for the first strongly correlated topological insulator. Such materials promise entirely new properties such as correlation-enhanced bulk bandgaps or a Fermi surface from spin excitations. Whether SmB6 and its surface states are topological or trivial is still heavily disputed however, and a solution is hindered by major disagreement between angle-resolved photoemission (ARPES) and scanning tunneling microscopy (STM) results. Here, a combined ARPES and STM experiment is conducted. It is discovered that the STM contrast strongly depends on the bias voltage and reverses its sign beyond 1 V. It is shown that the understanding of this contrast reversal is the clue to resolving the discrepancy between ARPES and STM results. In particular, the scanning tunneling spectra reflect a low-energy electronic structure at the surface, which supports a trivial origin of the surface states and the surface metallicity of SmB6. |
| Keywords: | heavy fermions photoemission scanning tunneling microscopy topological insulators |