Mooshammer, Fabian and Sandner, Fabian and Huber, Markus A. and Zizlsperger, Martin and Weigand, Helena and Plankl, Markus and Weyrich, Christian and Lanius, Martin and Kampmeier, Joern and Mussler, Gregor and Gruetzmacher, Detlev and Boland, Jessica L. and Cocker, Tyler L. and Huber, Rupert (2018) Nanoscale Near-Field Tomography of Surface States on (Bi(0.5)b(0.5))(2)Te-3. NANO LETTERS, 18 (12). pp. 7515-7523. ISSN 1530-6984, 1530-6992
Full text not available from this repository. (Request a copy)Abstract
Three-dimensional topological insulators (TIs) have attracted tremendous interest for their possibility to host massless Dirac Fermions in topologically protected surface states (TSSs), which may enable new kinds of high-speed electronics. However, recent reports have outlined the importance of band bending effects within these materials, which results in an additional two-dimensional electron gas (2DEG) with finite mass at the surface. TI surfaces are also known to be highly inhomogeneous on the nanoscale, which is masked in conventional far-field studies. Here, we use near-field microscopy in the mid infrared spectral range to probe the local surface properties of customtailored (Bi0.5Sb0.5)(2)Te-3 structures with nanometer precision in all three spatial dimensions. Applying nanotomography and nanospectroscopy, we reveal a few-nanometer-thick layer of high surface conductivity and retrieve its local dielectric function without assuming any model for the spectral response. This allows us to directly distinguish between different types of surface states. An intersubband transition within the massive 2DEG formed by quantum confinement in the bent conduction band manifests itself as a sharp, surface-bound, Lorentzian-shaped resonance. An additional broadband background in the imaginary part of the dielectric function may be caused by the TSS. Tracing the intersubband resonance with nanometer spatial precision, we observe changes of its frequency, likely originating from local variations of doping or/and the mixing ratio between Bi and Sb. Our results highlight the importance of studying the surfaces of these novel materials on the nanoscale to directly access the local optical and electronic properties via the dielectric function.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | 3-DIMENSIONAL TOPOLOGICAL INSULATOR; ANALYTICAL-MODEL; DIRAC PLASMONS; FLOQUET-BLOCH; SCATTERING; BI2TE3; SB2TE3; BI2SE3; PHOTOCURRENTS; SPECTROSCOPY; Near-field microscopy; SNOM; tomography; topological insulator; surface state; band bending |
| Subjects: | 500 Science > 530 Physics |
| Divisions: | Physics > Institute of Experimental and Applied Physics > Chair Professor Huber > Group Rupert Huber |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 04 Oct 2019 08:52 |
| Last Modified: | 04 Oct 2019 08:52 |
| URI: | https://pred.uni-regensburg.de/id/eprint/13418 |
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