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CPM SeminarMeasuring the Quantum Hall effect without contactsMartin ElliottCardiff UniversityIf a two-dimensional electron gas is subject to a sweeping magnetic field, eddy currents are induced. These eddy currents are largest near integer (and fractional) filling factors where the longitudinal resistivity tends to zero at low temperature. By detecting the eddy currents via their magnetic moment we can make a contact-free measurement of the Quantum Hall effect. I shall present three main sets of results which show that (1) at elevated temperature a simple semi-classical description of the QHE eddy currents can be used (2) at lower temperatures the semi-classical picture must be modified to include edge capacitance (3) for large enough induced currents a dramatic breakdown of the QHE is observed. The breakdown is particulary interesting in showing, depending on the sample and sample history, both stochastic breakdown with a power-law distribution and a Laughlin-like charge up of the sample edge.
Friday, May 9th 2003, 15:30
Ernest Rutherford Physics Building, R.E. Bell Conference Room (room 103) |