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Measurement of the topological surface state optical conductance in bulk-insulating Sn-doped Bi1.1Sb0.9Te2 S single crystals

Author(s): Cheng, Bing; Wu, Liang; Kushwaha, Satya Kumar; Cava, Robert Joseph; Armitage, N. Peter

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Abstract: Topological surface states have been extensively observed via optics in thin films of topological insulators. However, in typical thick single crystals of these materials, bulk states are dominant and it is difficult for optics to verify the existence of topological surface states definitively. In this Rapid Communication, we study the charge dynamics of the newly formulated bulk-insulating Sn-doped Bi1.1Sb0.9Te2S crystal by using time-domain terahertz spectroscopy. This compound shows much better insulating behavior than any other bulk-insulating topological insulators reported previously. The transmission can be enhanced an amount which is 5% of the zero-field transmission by applying magnetic field to 7 T, an effect which we believe is due to the suppression of topological surface states. This suppression is essentially independent of the thicknesses of the samples, showing the two-dimensional nature of the transport. The suppression of surface states in field allows us to use the crystal slab itself as a reference sample to extract the surface conductance, mobility, charge density, and scattering rate. Our measurements set the stage for the investigation of phenomena out of the semiclassical regime, such as the topological magnetoelectric effect. © 2016 American Physical Society.
Publication Date: Nov-2016
Electronic Publication Date: 22-Nov-2016
Citation: Cheng, Bing, Wu, Liang, Kushwaha, Satya K., Cava, Robert J., Armitage, N. Peter (2016). Measurement of the topological surface state optical conductance in bulk-insulating Sn-doped Bi1.1Sb0.9Te2 S single crystals. Physical Review B, 94 (20), 10.1103/PhysRevB.94.201117
DOI: doi:10.1103/PhysRevB.94.201117
ISSN: 2469-9950
EISSN: 2469-9969
Pages: 94.20:201117-1 - 201117-5
Type of Material: Journal Article
Journal/Proceeding Title: Physical Review B
Version: Final published version. This is an open access article.
Notes: Physical Review B. Volume 94, Issue 20, 22 November 2016, Article number 201117.

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