STM and STS studies of electronic states near macroscopic defects in topological insulators
Abstract/Contents
- Abstract
- Bi2Te3 and Bi2Se3 have been argued to be 3D topological insulators, exhibiting a bulk gap and a single, non-degenerate Dirac fermion surface band topologically protected by time-reversal symmetry. In this dissertation we will discuss the physics of topological insulators. We will show that scanning tunneling spectroscopy studies on high-quality Bi2Te3 and Bi2Se3 crystals exhibit perfect correspondence to ARPES data, hence enabling identification of different regimes measured in the local density of states. Unique to Bi2Te3, we will discuss observation of oscillations of LDOS near a step. Within the main part of the surface band we found that the oscillations are strongly damped, supporting the hypothesis of topological protection. At higher energies, as the surface band becomes concave, oscillations appear which disperse with a particular wave-vector that results from an unconventional hexagonal warping term in the surface-state-band Hamiltonian. For both systems, a "bound state" was observed in the bulk gap region that runs parallel to the edge of the defect and is bound to it at some characteristic distance. An expression that fits the data, and provides insight into the general properties of the surface band near strong structural defects, can be obtained using the full three-dimensional Hamiltonian of the system. In the case of Bi2Se3 whose band structure doesn't exhibit warping we studied the effect of local defects (impurities) on the local density of states. Although no visible interference pattern was detected we observed resonances localized around the defects. Such resonances agree quantitatively with a theory due Biswas and Balatsky which treats impurities as local potential wells interacting with a 2D Dirac gas which models the surface state of a topological insulator.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2012 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Alpichshev, Zhanybek |
|---|---|
| Associated with | Stanford University, Department of Physics |
| Primary advisor | Kapitulnik, Aharon |
| Thesis advisor | Kapitulnik, Aharon |
| Thesis advisor | Fisher, Ian R. (Ian Randal) |
| Thesis advisor | Qi, Xiaoliang |
| Advisor | Fisher, Ian R. (Ian Randal) |
| Advisor | Qi, Xiaoliang |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Zhanybek Alpichshev. |
|---|---|
| Note | Submitted to the Department of Physics. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2012. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2012 by Zhanybek Alpichshev
- License
- This work is licensed under a Creative Commons Attribution 3.0 Unported license (CC BY).
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