Edge magnetoplasmons (EMPs) and pinning mode resonances in two dimensional electron systems (2DESs) can both be thought of as lower hybrid modes of cyclotron and plasma resonances. This dissertation describes low temperature microwave spectroscopy of both of these modes. EMPs have oscillating charge confined at the 2DES edge by the combination of the perpendicular magnetic field and the electrostatic potential that produces the edge. Pinning mode resonances are from electron solids oscillating against confinement provided by disorder in the bulk of the 2DES.
The first part of this dissertation concerns the search for a mode similar to an EMP but confined solely by a linear magnetic inhomogeneity in the perpendicular magnetic field (Bz). While we do not observe such an excitation, we do observe a marked reduction in the velocity of an EMP in the presence of a Bz-inhomogeneity.
In the second part of this dissertation, we investigate pinning modes in “wide'' quantum well samples, for which the effective electron-electron interaction is softened at short range due to the vertical extent of the wavefunction. We observe a pinning mode resonance whose peak frequency (fpk ) vs Landau level filling (ν) shows an anomalous increase as ν moves away from ν = 1 under roughly the same conditions as anomalous quantum Hall effects observed previously in DC transport. A region of ν with enhanced fpk is interpreted as evidence for a new electron solid phase.
|Advisor:||Engel, Lloyd W.|
|Commitee:||Bonesteel, Nick, Strauss, Geoffry, Wiedenhover, Ingo, Xiong, Peng|
|School:||The Florida State University|
|School Location:||United States -- Florida|
|Source:||DAI-B 74/10(E), Dissertation Abstracts International|
|Subjects:||Electromagnetics, Condensed matter physics|
|Keywords:||Edge magnetoplasmons, Electron solid, Quantum Hall effect, Two dimensional electron system, Wigner crystals|
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