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Josephson effect

  1. Sep 16, 2011 #1
    Hi,

    I am confused about josephson effect. Take SNS for example. If the phase of these two superconductors are different, then there will be a josephson current through the junction. Experimentally, do we measure the current by attach two ends of SNS with a wire? If there is no wire attached to these two ends, will there be a current flowing through the junction? In other words, will there be a self-generated current in it without a loop?

    Thanks for you help.
     
  2. jcsd
  3. Sep 16, 2011 #2

    f95toli

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    Yes, you measure it by passing a current through the junction and then measuring the voltage across it.

    And no, there won't be "self generated" current.
    The only time you would get a current through a junction not connected by a wire is if it is part of a loop that is being threaded by a changing flux (i.e. an RF- SQUID).
     
  4. Sep 16, 2011 #3
    Thanks for your quick reply. Now I am confused about your statement "measure it by passing a current through the junction and then measuring the voltage across it." It means we have to pass a current through the junction, otherwise there will be no current? Is it correct. Thanks.
     
  5. Sep 17, 2011 #4

    f95toli

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    Yes, the current-voltage characheristics of JJs are measured in exactly the same way as for example semiconductor diods; you use current source to bias it and then a voltmeter to measure the voltage across it (you can do it the other way aorund, using a voltage source and an ammeter; but this is quite tricky since the impedance of the junction is practically zero when you are on the supercurrent branch).
     
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