We retrieved the nanoscale dielectric function of surface states on a three-dimensional topological insulator, which was grown in the group of Dr. Gregor Mussler and Prof. Dr. Detlev Grützmacher at Forschungszentrum Jülich. In collaboration with Tyler Cocker from the Michigan State University, we succeeded in identifying two types of surface states by employing near-field tomography: a massive, two-dimensional electron gas giving rise to an intersubband transition in the multi-THz range as well as indications of the topologically protected surface states in the form of a broadband absorption background.
Fabian Mooshammer, Fabian Sandner, Markus A. Huber, Martin Zizlsperger, Helena Weigand, Markus Plankl,
Ch. Weyrich, M. Lanius, J. Kampmeier, G. Mussler, D. Grützmacher, J. L. Boland, T. L. Cocker, and R. Huber.
Nano Lett 18, 7515–7523 (2018).