Unconventional superconductors and interplay with spin-orbit coupling, magnetism, and electronic interactions
Abstract/Contents
- Abstract
- It can be said that a lot of present day research on superconductivity is focused on unconventional superconductors. That is not surprising given that any non-s-wave superconductor is strictly speaking unconventional, from the high-Tc cuprates to heavy fermion superconductors, among many classes. As such, interesting, unsolved puzzles are often found in unconventional superconducting systems. For example, there is still no consensus on why the superconducting dome in SrTiO3 exists, or what the symmetry of the pairing state in Sr2RuO4 is. In this thesis, we will study various examples of unconventional superconductors and how their behaviors are driven and affected by interactions such as spin-orbit coupling, external magnetic fields, and atomic electronic interactions. While our main focus will be on unconventional superconducting systems, we will also delve a bit into the half-filled Landau level problem towards the end. The first part of this thesis focuses on how spin-orbit coupling and atomic interactions interplay to affect the kinds of on-site superconducting pairing states that are allowed by symmetry. Using group theory and mean field equations, we deduce the conditions under which spin triplet, orbital singlet on-site pairing states can be stabilized in multi-orbital d-electron based systems. Having theoretically studied one of the effects of spin-orbit coupling on superconductivity, we then switch our setting to the laboratory where we discover that spin-orbit coupling can be a significant energy scale -- of the order of the superconducting gap -- in epitaxially grown strontium titanate. The strength of the spin-orbit scattering rate leads to surprising behavior of the superconducting tunneling spectrum. Next, we turn to an entirely separate class of unconventional superconductors -- the uranium based heavy fermion superconductor UCoGe where we again apply group theory and Landau theory analyses to make predictions on the phase diagram of this system. The phase diagram of UCoGe permits coexistence of superconductivity and ferromagnetism. We study the nature of the phase transitions between the superconducting, ferromagnetic, and coexisting phases. In the final part of this thesis, we switch gears entirely and study the quantum oscillations near the half-filled Landau level in a two dimensional electron gas under a period electric potential. We uncover surprising results regarding the relationship between relativistic and non-relativistic theories for the half-filled Landau level.
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 | Cheung, Alfred Ka Chun |
|---|---|
| Degree supervisor | Raghu, Srinivas, 1978- |
| Thesis advisor | Raghu, Srinivas, 1978- |
| Thesis advisor | Hwang, Harold Yoonsung, 1970- |
| Thesis advisor | Kivelson, Steven |
| Degree committee member | Hwang, Harold Yoonsung, 1970- |
| Degree committee member | Kivelson, Steven |
| Associated with | Stanford University, Department of Physics. |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Alfred Cheung. |
|---|---|
| Note | Submitted to the Department of Physics. |
| Thesis | Thesis Ph.D. Stanford University 2019. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2019 by Alfred Ka Chun Cheung
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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