Scientists at the Georgia Institute of Technology have discovered a phenomenon which allows measurement of the mechanical motion of nanostructures by using the AC Josephson effect. The findings, which may be used to identify and characterize structural and mechanical properties of nanoparticles, including materials of biological interest, appear online in the journal Nature Nanotechnology.

The AC Josephson effect refers to work that Brian Josephson published in 1962 regarding the flow of an electrical current between superconductors. In this work, for which he shared a 1973 Nobel Prize, Josephson predicted that when a constant voltage difference is maintained across two weakly linked superconductors separated by a thin insulating barrier (an arrangement now known as a Josephson junction), an alternating electrical current would flow through the junction (imagine turning on a water faucet and having the water start flowing up as well as down once it leaves the spigot). The frequency of the current oscillations is directly related to the applied voltage.

These predictions were fully confirmed by an immense number of experiments, and the standard volt is now defined in terms of the frequency of the Josephson AC current. The Josephson effect has numerous applications in physics, computing and sensing technologies. It can be used for ultra high sensitive detection of electromagnetic radiation, extremely weak magnetic fields and in superconducting quantum computing bits.

Now, experimental physicist Alexei Marchenkov and theoretician Uzi Landman at Georgia Tech have discovered that the AC Josephson effect can be used to detect mechanical motion of atoms placed in the Josephson junction.

"We show here that in addition to being able to detect the effects of electromagnetic radiation on the AC Josephson current, one can also use it to probe mechanical motions of atoms or molecules placed in the junction, said Landman, directo
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Contact: David Terraso
d.terraso@gatech.edu
404-385-2966
Georgia Institute of Technology
24-Jul-2007