Liu, Lei;
(2023)
Non-Magnetic Fractional Conductance Quantization in InGaAs/GaAs Nanostructures.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
This thesis describes two important experimental results of non-magnetic fractional quantized conductance in quasi-one-dimensional quantum wires, indicating the importance of electron-electron interaction in the formation of fractional quantum states. The quasi-1D quantum wires are defined using split-gate top-gate design and are fabricated from high mobility two-dimensional electron gases formed in In0.75Ga0.25As/GaAs heterostructures. Especially, spin-orbit coupling is introduced into the system and its influence on fractional quantum states is studied systematically. The first experimental result (reported in chapter 5) describes a significant feature, 0.2(e2/h), that is commonly observed in different devices during different cooldowns. This conductance value, 0.2(e2/h), as well as its temperature dependence are already predicted by Shavit and Oreg [1]. However, it is the first time to directly observe how strong spin-orbit coupling affects fractional quantization by studying its field dependence and asymmetry dependence. The second experimental result (reported in chapter 6) focuses on another distinct feature, 0.1(e2/h), which is often observed when the sample is fully illuminated and scattering effects are minimized. It is the first time to observe this even denominator fraction in InGaAs system, though it is already predicted by Shavit and Oreg. Spin-orbit coupling is again proved to play a vital role in the formation of this fractional quantum state by studying its asymmetry dependence as well as magnetic field dependence. In this thesis, we prove that fractional quantized conductance can be observed at low carrier density when lateral confinement is weakened to allow electron repulsion to dominate. Also, the importance of strong spin-orbit modification of interaction in 1D quantum transport is emphasized by performing systematic experiments on varying Rashba effects. We believe the new quantum state described here will help with the fundamental understanding of low-dimensional electron systems, and may enable further development of future quantum structures.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Non-Magnetic Fractional Conductance Quantization in InGaAs/GaAs Nanostructures |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2023. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Electronic and Electrical Eng |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10173638 |
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