Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

What's with 'virtual' phonons in BCS pairing?

  1. Sep 30, 2013 #1
    Can someone explain why virtual phonons are necessary to explain BCS pairing in type I superconductors. I thought phonons originated with the lattice vibrations. I read that it s the 'virtual" phonons that explains the pairing; how so? what am I missing ?
     
  2. jcsd
  3. Sep 30, 2013 #2

    DrDu

    User Avatar
    Science Advisor

    Real phonons are lattice deformations which can propagate freely, i.e. sound waves.
    Virtual phonons are needed to describe e.g. static lattice deformations surrounding a perturbation, e.g. an electron. In the most simple limit this gives the rubber surface description of Cooper pairing: An electron behaves like a ball on a rubber surface, it creates a deformation of the surface and a second electron (ball) will fall into that hole.
     
  4. Sep 30, 2013 #3

    ZapperZ

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor
    2016 Award

    You are missing Quantum Field Theory.

    The idea here is that one is trying to describe the interaction between two objects. Naively, in QFT, this is accomplished via the exchange of a virtual bosonic "particle". In E&M, it is the exchange of virtual photon. In condensed matter physics, it can be any boson that is the equivalent of a 'vacuum excitation'. In the case of conventional superconductivity, this is the virtual phonons.

    In other cases, you can have an exchange of magnons, polarons, etc...

    Zz.
     
  5. Sep 30, 2013 #4
    Thank you both for the replies. So the pairing is a result mostly of the virtual phonon exchange, and not the real phonons that originate in the lattice...or both? Can either of you describe the effect of each if possible.
    2. So is it the virtual momentum exchange that causes the attractive potential,?
    Thanks.
     
  6. Jan 24, 2017 #5
    if quantum tunneling is involved its all virtual
     
  7. Jan 24, 2017 #6

    ZapperZ

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor
    2016 Award

    No it doesn't. Show me the physics that says this.

    This is also a necropost.

    Zz.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: What's with 'virtual' phonons in BCS pairing?
  1. What is a phonon? (Replies: 3)

  2. Cooper pairs and BCS (Replies: 2)

  3. What is a phonon? (Replies: 4)

Loading...