Dr. Ramesh Mani
, Harvard University
[Host: Paul Fendley]
We report the experimental detection of novel zero-resistance states
, which are induced by electromagnetic wave excitation in ultra
high mobility GaAs/AlGaAs heterostructure devices including a
two-dimensional electron system. Radiation-induced
vanishing-resistance states, which do not exhibit concomitant Hall
resistance quantization, are demonstrated in the large filling factor,
low magnetic field limit, at liquid helium temperatures. It is shown
that the observed resistance minima follow the series B = [4/(4j+1)]
Bf with j=1,2,â¦, where Bf = 2fm*/e, m* is an effective mass, e is
electron charge, and f is the radiation frequency. These
resistance-minima exhibit an activated resistance as a function of the
temperature that leads into zero-resistance states at the lowest
temperatures. The dependence of the effect is reported as a function
of experimental parameters such as the electromagnetic wave frequency,
incident power, temperature, and the current.
 R. G. Mani, J. H. Smet, K. von Klitzing, V. Narayanamurti,
W. B. Johnson, and V. Umansky, Nature 420, 646 (2002).
Condensed Matter Seminar
Thursday, October 23, 2003
Physics Building, Room 204
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