In January 2007, Marchenkov and Landman published a paper in Physical Review Letters detailing their discovery that fluctuations in the conductance of ultra-thin niobium nanowires are caused by a pair of atoms, known as a dimer, shuttling back and forth between the bulk electrical leads.
In this latest research, Marchenkov and Landman, along with their collaborators Zhenting Dai, Brandon Donehoo and Robert Barnett, report that when a microfabricated junction assembly is held below its superconducting transition temperature, unusual features are found in traces of the electrical conductance measured as a function of the applied voltage.
In our experiments, only nanowires - which we know now to contain a single dimer have consistently shown a series of additional peaks in the conductance versus voltage curves. Since a peak in such measurements signifies a resonance and knowing that we have intrinsic high-frequency Josephson current oscillations, we started looking into the possible physical mechanisms, said Marchenkov, assistant professor in the School of Physics.
The team hypothesized that the new measured peaks likely originate from mechanical motions of the dimer, which causes enhancement of the electrical current at particular values of the applied voltage. At each of the peak voltages, the frequency of the AC Josephson current would resonate with the vibrational frequency of the nanostructure in the junction.
Subsequent first principles calculations by Landman's team predicted that such peaks would occur at three different frequencies, or voltages, and their integer multiples. One corresponds to a back and forth vibration of the dimer suspended between the two niob
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Contact: David Terraso
d.terraso@gatech.edu
404-385-2966
Georgia Institute of Technology
24-Jul-2007