Frictional drag in coupled mesoscopic systems

    Project Details


    In frictional drag experiments, a pair of independently contacted mesoscopic systems (quantum wells, quantum wires etc) are placed a few hundred Å apart. Current is driven through one subsystem and, due to the proximity of the systems, the coupling forces cause a measurable voltage build-up, or an induced current, in the other subsystem. This provides a unique opportunity for a transport measurement to probe interparticle interactions, and it gives important insights to the properties of the dimensionally restricted interacting electron systems.
    K. Flensberg and Ben Hu showed that, at intermediate temperatures, collective modes of the coupled electron system can enhance the Coulomb drag rate by almost an order of magnitude over previous predictions.
    Together with M. C. Bønsager (then a student at MIC), KF, APJ and BH theoretically studied the complex magnetic-field dependence of the drag transresistivity, including large enhancements and effects due to the interplay of the Landau level quantization and screening of the inter-well interaction. Lastly, BH, MCB, KF, AMD have studied the role of phonons mediating the drag, and we have proposed that a coupled transresistivity, which may explain the anomalously large magnitude of the experimental observations of phonon-mediated drag.
    We are continuing to study various aspects of frictional drag, such as the serach for a theory to explain the observation by J. Eisenstein (Cal Tech) of a nonvanishing frictional drag to T = 0 in u = 2 fractional quantum hall effect samples, which seems to contradict currently accepted theoretical models.
    Another example is mesocscopic Coulomb drag: we expect that the finite size will give rize to interesting fluctuation properties. Niels Asger Mortensen is looking at this problem as a part of his ph.d study, supervised by APJ and KF.
    Effective start/end date01/01/199731/12/2000


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