Quantum coherence and interactions in quantum dots
Abstract/Contents
- Abstract
- The behavior of electrons in solid state systems is determined by the interaction of their charge and spin degrees of freedom with each other and with the degrees of freedom of their environment. Whether the interactions manifest themselves by modifying some of the system's properties such as the effective mass in the Fermi liquid picture, or more directly by suppressing transport in the Coulomb blockade model, depends on the details and complexity of the system. This thesis investigates two cases: the Fermi liquid behavior in a system with exchange interactions (the spin 1/2 Kondo model) and effect of Coulomb interactions on the phase coherence of electrons in a quantum dot with single mode leads. The first experiment tests the Fermi liquid theory prediction of a quadratic power law dependence of the electron scattering rate on energy in the non-equilibrium regime. We measure transport though a lateral GaAs/AlGaAs quantum dot that acts as an artificial magnetic impurity coupled to a single reservoir and find that the low energy conductance obeys universal scaling with temperature and bias with a quadratic exponent as expected for the single channel Kondo state. This single particle picture fails when a second independent channel is added and the quantum correlations lead to non-Fermi liquid behavior. To understand how the short range Coulomb repulsion affects phase coherence we measure the quantum correction due to the weak localization of electrons in a quantum dot coupled to a reservoir via perfectly transmitting quantum point contacts. We extract the dephasing time and observe that it continues to increase down to the lowest temperatures, in accordance with the predictions from Fermi liquid theory and in contradiction with previous experiments in zero-dimensional structures. When the phase coherence time of the electrons becomes large enough, we observe the effects of the long range Coulomb repulsion as Coulomb blockade emerges. This was previously assumed to be characteristic of transport through quantum dots with tunneling quantum point contacts (QPCs). We show that despite the fully open QPCs of our device, the coherent backscattering of electrons at zero magnetic field is responsible for Coulomb charging effects and estimate that the residual charge quantization at the lowest temperature is 1/3 electron charge via charge sensing measurements.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2011 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Rau, Ileana Georgeta |
|---|---|
| Associated with | Stanford University, Department of Applied Physics |
| Primary advisor | Fisher, Ian R. (Ian Randal) |
| Primary advisor | Goldhaber-Gordon, David, 1972- |
| Thesis advisor | Fisher, Ian R. (Ian Randal) |
| Thesis advisor | Goldhaber-Gordon, David, 1972- |
| Thesis advisor | Kivelson, Steven |
| Advisor | Kivelson, Steven |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Ileana Georgeta Rau. |
|---|---|
| Note | Submitted to the Department of Applied Physics. |
| Thesis | Ph.D. Stanford University 2011 |
| Location | electronic resource |
Access conditions
- Copyright
- © 2011 by Ileana Georgeta Rau
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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