Recent theoretical and experimental studies suggest that SmB6 is the first topological Kondo insulator: A material in which the interaction between localized and itinerant electrons renders the bulk insulating at low temperature, while topological surface states leave the surface metallic. While this would elegantly explain the material's puzzling conductivity, we find the experimentally observed candidates for both predicted topological surface states to be of trivial character instead: The surface state at Γˉ is very heavy and shallow with a mere ∼2 meV binding energy. It exhibits large Rashba splitting which excludes a topological nature. We further demonstrate that the other metallic surface state, located at Xˉ, is not an independent in-gap state as supposed previously, but part of a massive band with much higher binding energy (1.7 eV). We show that it remains metallic down to 1 K due to reduced hybridization with the energy-shifted surface 4f level.
@article{arxiv.1502.01542,
title = {Samarium hexaboride: A trivial surface conductor},
author = {P. Hlawenka and K. Siemensmeyer and E. Weschke and A. Varykhalov and J. Sánchez-Barriga and N. Y. Shitsevalova and A. V. Dukhnenko and V. B. Filipov and S. Gabáni and K. Flachbart and O. Rader and E. D. L. Rienks},
journal= {arXiv preprint arXiv:1502.01542},
year = {2018}
}