Study of Nonlocal Quantum Effects in High-Mobility Two Dimensional Electron Gas.
Abstract
By measuring a high electron mobility semiconductor in a nonlocal configuration several interesting quantum effects were observed. In a nonlocal measurement the current and voltage leads are physically separated so that the current does not intersect the voltage probes in a classical sense. The decay length of Shubnikov-deHaas peaks was observed to increase as the magnetic field increases. The decay length was measured to be of the order of tens of micrometers, which has been observed for adiabatic transport in edge channels but was not expected for electron transport in the bulk of the Landau levels. In measurements in which a gate lay between the current and voltage probes, Shubnikov -deHaas peaks were observed if the bulk Landau levels aligned at the Fermi energy in the gated and ungated regions, though it was not necessary for them to be the same index Landau levels. This indicates that electrons were able to tunnel between different Landau levels in the gated and ungated regions. If the Landau levels were misaligned, the magnitude of the Shubnikov-deHaas peak was reduced, depending on the degree of separation. Measurement of universal conductance fluctuations showed no change in the "period" of the fluctuations and a small increase in the magnitude of the fluctuations, not in accord with results obtained with similar measurements in quantum wires.
- Publication:
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Ph.D. Thesis
- Pub Date:
- 1994
- Bibcode:
- 1994PhDT........42D
- Keywords:
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- Engineering: Electronics and Electrical; Physics: Electricity and Magnetism