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3 results on '"topological surface states"'

1. Faraday Rotation Due to Surface States in the Topological Insulator (Bi1–x Sb x )2Te3

Author

Shao, Yinming, Post, Kirk W, Wu, Jhih-Sheng, Dai, Siyuan, Frenzel, Alex J, Richardella, Anthony R, Lee, Joon Sue, Samarth, Nitin, Fogler, Michael M, Balatsky, Alexander V, Kharzeev, Dmitri E, and Basov, DN

Subjects
Bismuth antimony telluride, topological insulators, cyclotron resonance, Faraday rotation, topological surface states, cond-mat.mes-hall, hep-ph, Nanoscience & Nanotechnology
Abstract

Using magneto-infrared spectroscopy, we have explored the charge dynamics of (Bi,Sb)2Te3 thin films on InP substrates. From the magneto-transmission data we extracted three distinct cyclotron resonance (CR) energies that are all apparent in the broad band Faraday rotation (FR) spectra. This comprehensive FR-CR data set has allowed us to isolate the response of the bulk states from the intrinsic surface states associated with both the top and bottom surfaces of the film. The FR data uncovered that electron- and hole-type Dirac Fermions reside on opposite surfaces of our films, which paves the way for observing many exotic quantum phenomena in topological insulators.

Published
2017

2. Faraday Rotation Due to Surface States in the Topological Insulator (Bi1-xSbx)2Te3.

Author

Shao, Yinming, Post, Kirk W, Wu, Jhih-Sheng, Dai, Siyuan, Frenzel, Alex J, Richardella, Anthony R, Lee, Joon Sue, Samarth, Nitin, Fogler, Michael M, Balatsky, Alexander V, Kharzeev, Dmitri E, and Basov, DN

Subjects
Bismuth antimony telluride, Faraday rotation, cyclotron resonance, topological insulators, topological surface states, cond-mat.mes-hall, hep-ph, MD Multidisciplinary, Nanoscience & Nanotechnology
Abstract

Using magneto-infrared spectroscopy, we have explored the charge dynamics of (Bi,Sb)2Te3 thin films on InP substrates. From the magneto-transmission data we extracted three distinct cyclotron resonance (CR) energies that are all apparent in the broad band Faraday rotation (FR) spectra. This comprehensive FR-CR data set has allowed us to isolate the response of the bulk states from the intrinsic surface states associated with both the top and bottom surfaces of the film. The FR data uncovered that electron- and hole-type Dirac Fermions reside on opposite surfaces of our films, which paves the way for observing many exotic quantum phenomena in topological insulators.

Published
2017

3. Atomic and Electronic Structures of Bismuth Selenide Surfaces Investigated by Low Energy Ion Scattering

Author

Zhou, Weimin

Subjects
Condensed matter physics, Physics, Bismuth Selenide, charge exchange, impact collision ion scattering spectroscopy, low energy ion scattering, surface structure, topological surface states
Abstract

Topological insulator (TI) materials do not conduct electricity in the bulk, but instead conduct along the surface via topological surface states (TSS). To fully utilize these materials, it is critically important to understand their surface atomic and electronic structures, both of which can be sensitively probed by low energy ion scattering (LEIS). Bi2Se3 is a TI that consists of stacked quintuple layers ordered as Se-Bi-Se-Bi-Se. The surfaces are expected to show a Se-termination after mechanical cleaving, but instead various surface terminations are found. Time-of-flight (TOF) LEIS spectra show that Bi2Se3 surfaces prepared by in situ cleaving or by Ar+ ion bombardment and annealing (IBA) are always Se-terminated. Impact collision ion scattering spectroscopy (ICISS) finds no differences in the geometric structure of the top three atomic layers of IBA-prepared surfaces and in situ cleaved surfaces. Note that the annealing temperature is critical in preparing surfaces with IBA. If it’s too low, then surface will not be well-ordered. If it’s too high, then surface Se vacancies will form. Ex situ cleaved Bi2Se3 surfaces can be either Se-terminated or Bi-rich, which might be caused by contaminants that adsorb at surface defects and induce a chemical reaction. After exposure to air, IBA-prepared surfaces show less surface contamination than cleaved surfaces and maintain their Se-termination. Cs is adsorbed on Bi2Se3 as a tool to investigate the surface electronic properties of TIs. Scattered alkali ions exchange charge with surfaces through a non-adiabatic resonant charge transfer (RCT) process that depends on the local electrostatic potential (LEP) above the target atom. It is found that the neutralization probability for Na+ scattered from Se sites is unexpectedly larger than from Bi sites. This can be explained by the spatial distribution of the TSS carriers in which the electron density accumulates below the first layer Se atoms and above the second layer Bi. This spatial distribution leads to an upward pointing dipole on Se sites that reduces the LEP and a downward dipole above Bi that increases the LEP.

Published
2016

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