Novel phenomena driven by interactions and symmetry breaking in graphene
Abstract/Contents
- Abstract
- The electronic properties of graphene are well described by a non-interacting Dirac Hamiltonian with an internal symmetry associated with spin and valley, an additional degree of freedom due to the hexagonal crystal lattice of graphene. As a result, graphene exhibits a variety of peculiar phenomena such as an anomalous quantum Hall effect or the absence of backscattering. However, this model breaks down in extremely clean samples, as interactions between electrons and with the substrate become relevant. In this work, we discuss some of the properties of graphene and boron nitride heterostructures, in particular the patterns of broken symmetry phases one can observe in these devices. First, we observe modification in the electronic band structure of graphene due to its interactions with the substrate. The sub lattice symmetry of the Dirac Hamiltonian is broken, which opens an energy gap at charge neutrality, in addition to superlattice Dirac points due to the moire pattern that graphene forms on boron nitride. We then describe transport at high magnetic field, in the quantum Hall regime, where Coulomb interactions yield spin and valley quantum Hall ferromagnetic phases, with polarized one dimensional states propagating along the edges of the device. Using dual-gated device geometries, we can address the transport properties of these edge states and in particular how they equilibrate, depending on their polarization (or absence thereof). At even higher fields, new collective ground states emerge in the fractional quantum Hall regime. In extremely clean samples we observe a plethora of fractional quantum Hall states, described by the composite fermion theory, with unexpected patterns of stability and spin polarizations. Observing these electronic phenomena requires an outstanding device quality with carrier mobility exceeding one million cm2/Vs. We describe in this work the fabrication and characterization methods that allow us to control the quality of graphene/boron nitride, as well as novel device geometries allowing for high quality bipolar transport in graphene.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2014 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Amet, François |
|---|---|
| Associated with | Stanford University, Department of Applied Physics. |
| Primary advisor | Goldhaber-Gordon, David, 1972- |
| Primary advisor | Kapitulnik, Aharon |
| Thesis advisor | Goldhaber-Gordon, David, 1972- |
| Thesis advisor | Kapitulnik, Aharon |
| Thesis advisor | Hwang, Harold Yoonsung, 1970- |
| Advisor | Hwang, Harold Yoonsung, 1970- |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | François Amet. |
|---|---|
| Note | Submitted to the Department of Applied Physics. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2014. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2014 by Francois Alexis Gabriel Amet
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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