Electronic structure in strontium titanate probed by planar tunneling spectroscopy
Abstract/Contents
- Abstract
- SrTiO3 superconductivity has been studied for decades and still attracts much attention due to its uniqueness. The properties of superconductivity in SrTiO3 are two-sided; some aspects are conventional and others are not. Its carrier density is extremely low and outside of the adiabatic condition in the conventional BCS (Bardeen-Copper-Schrie er) theory for superconductivity in metals. Despite longstanding query, probing its electronic structure has been a challenge because of the large surface depletion layer, especially for the low carrier density regime. In this work, we examine the electronic structure of SrTiO3 for the entire superconducting dome probed by planar tunneling spectroscopy. The suppression of the problematic depletion layer was achieved by using a polar oxide (LaAlO3) as a tunnel barrier. The atomically precise band engineering enabled the construction of a high-quality tunnel junction in electron-doped SrTiO3, which produced the high-resolution tunneling spectra. The evolution of tunneling spectra demonstrates that superconducting electrons are weakly coupled to pairing bosons while normal state electrons are strongly coupled to the longitudinal phonons. The transverse optic soft phonon is suggested as a possible candidate for pairing to explain this discrepancy in the adiabatic condition. How the transverse mode can couple to electrons in this inversion symmetric system still remains unclear, and this can be a unique feature in this incipient ferroelectric system. Furthermore, the physics of SrTiO3 tunneling devices are discussed in this thesis. First, the origins and control of the depletion width in electron-doped SrTiO3 were studied. In addition, LaAlO3, which is used to suppress the depletion width, can accumulate electrons at the interface with electron-doped SrTiO3. The detection and control of electron accumulation are presented, and these are essential to obtain high-quality tunnel junctions to probe the low-density SrTiO3 of interest.
Description
| Type of resource | text |
|---|---|
| Form | electronic resource; remote; computer; online resource |
| Extent | 1 online resource. |
| Place | California |
| Place | [Stanford, California] |
| Publisher | [Stanford University] |
| Copyright date | 2019; ©2019 |
| Publication date | 2019; 2019 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Author | Yoon, Hyeok |
|---|---|
| Degree supervisor | Hwang, Harold Yoonsung, 1970- |
| Thesis advisor | Hwang, Harold Yoonsung, 1970- |
| Thesis advisor | Raghu, Srinivas, 1978- |
| Thesis advisor | Suzuki, Yuri, (Applied physicist) |
| Degree committee member | Raghu, Srinivas, 1978- |
| Degree committee member | Suzuki, Yuri, (Applied physicist) |
| Associated with | Stanford University, Department of Applied Physics. |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Hyeok Yoon. |
|---|---|
| Note | Submitted to the Department of Applied Physics. |
| Thesis | Thesis Ph.D. Stanford University 2019. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2019 by Hyeok Yoon
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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