1. Phonons play two different roles in metals. At high temperatures, they scatter electrons, giving rise to electrical resistivity. At low temperatures, when a metal becomes a supeconductor, phonons bind pairs of electrons (Cooper Pairs), dropping the electrical resistance to zero. Phonons are a mathematical description of the vibrations of atoms in a crystal lattice. But are they real? That is, can they be detected outside the lattice in which they are supposedly created?
    In the early 1970s, I devised an experiment to determine whether phonons were real. The experiment involved superconducting tunneling junctions on opposite faces of a crystal; one junction to generate high energy phonons and the other to detect high energy phonons. I could 'dial in' the energies for generating and detecting phonons simply by applying voltages across superconducting tunnel junctions. If the detector registered a current when the voltage across the generator passed a predicted value, it would prove that phonons were real.
    The predictions and experiments were based on calculations performed using the BCS theory of superconductivity* and the discovery by Giaever** of electron tunneling in junctions, respectively.

    *Bardeen, Cooper, and Schrieffer received the Nobel Prize in 1972 for the development of the theory of superconductivity.
    **Giaever received the Nobel Prize in 1973 for his discovery of electron tunneling in superconductors.

    I chose Sn as the generator junction and Pb as the detector junction. High energy phonons could only be detected in Pb junctions when the voltage across the Sn junction was greater than 3.9 mV. At this voltage, an incoming phonon can break apart a Cooper pair in the Pb junction, releasing electrons to tunnel, producing a signal indicating 'phonon detection.'
    This dance depicts the interactions of electrons and phonons in metals in two acts. Act 1: the metal at high temperatures and the superconductor at low temperatures. Act 2: Generation and detection of phonons below and above 3.9 mV, the voltage delivering energy sufficient to break Cooper pairs.

    Credit

    Cast & Crew:
    Irwin Singer and Ron Singer: electrons
    Silvia Burstein-Hendi: lattice vibration and Cooper Pairer
    Paula Giammarco: lattice vibration
    Sara Lavan: lattice vibration
    Mary Jo Smet: lattice vibration and low energy phonon
    Melanie Tung: lattice vibration and high energy phonon
    Videographers: Mike and Melinda McMullin
    Audio: Joan Singer
    Creator, Choreographer and video editor: Irwin Singer
    Music: selections from Summer and Winter from The Four Seasons Concerto No.2, Antonio Vivaldi.

    Acknowledgements:
    Special thanks to Melanie, Silvia, Paula, Sara and Mary Jo from The Choreographers Collaboration Project, a modern dance company based in Alexandria, VA.
    To The City of Alexandria for allowing me to shot the video in racquetball court #3 at Chinquapin Recreation Center.
    To Maneesh Mishra from Prof. Izabela Szlufarska's group at U. Wisconsin, Madison, for atomistic simulations.

    Excerpted from the PhD thesis of Irwin L. Singer, Indiana University, Department of Physics, 1976. "Generation and Detection of High-Energy Phonons by Superconducting Junctions.“
    Peer-reviewed research article: I. L. Singer and W. E. Bron, Phys. Rev. B 14 (1976) 2832.
    After his PhD studies. Dr. Singer went to the US Naval Research Lab as a post-doc in 1976 and has been there ever since working as a Tribologist in the Chemistry Division.
    Submitted to the 2010 AAAS "Dance your PhD" Contest, 31 August 2010.
    All rights reserved. Batteries not included.

    # vimeo.com/14589849 Uploaded 11.8K Plays 0 Comments
  2. This is an outline of the story - Electrons and phonons in superconductors: A love story,, with animation for each of the 'acts.' We will choreograph this on sunday, 22 Aug, 1 - 4 pm.

    # vimeo.com/14273839 Uploaded 38 Plays 0 Comments
  3. Synopsis: Electrons in a metal can escape from the atoms that make up the metallic lattice and wander clustered like a gas through the metal. However, they are constantly crashing into each other and atoms on lattice sites, giving rise to electrical resistance. When the temperature gets cold enough in certain metals, two electrons can avoid crashing by joining together to make a Cooper pair. This threesome, two electrons and the phonon (a lattice vibration) that binds them, can move effortlessly without scattering in this superconducting world. But, if attacked by high energy electrons or phonons, the Cooper pair will be broken up into two independent electrons: most probably, one with high energy and the other with very little energy. But alas, nothing is forever, especially at finite temperatures, where high energy electrons and phonons lurk. The electrons are doomed to return to the jungle of lattice vibrations, hopeful that in a time constant or two they might be rejoined - like penguin lovers on ice - as a Cooper pair. The dance, a mix of Martha Graham-style shapes and tension and the sensuous flow of Argentine tango, contrasts the high-energy danger experienced by single electrons with the coherent calm of the Cooper pairs.

    Excerpted from the PhD thesis of Irwin L. Singer, Indiana University, Department of Physics, 1976. "Generation and Detection of High-Energy Phonons by Superconducting Junctions."
    Peer-reviewed research article: I. L. Singer and W. E. Bron, Phys. Rev. B 14 (1976) 2832.
    After his PhD studies. Dr. Singer went to the US Naval Research Lab as a post-doc in 1976. He became a staff member in 1978 and has been head of the Tribology Section in the Chemistry Division since 1984.

    Credits:
    Created by Irwin Singer
    Choreography and Dancers:
    Irwin Singer
    the lovely Carina
    Videographer: Luis Murray
    Video editor: Irwin Singer
    Music: Taquito Militar, by Mariano Mores
    Performed by QuinTango from their 2000 CD album, 'Secret Places'
    Special thanks to my wife, Joan Singer, who made it all possible.

    Submitted to the 2009 AAAS Science Dance Contest, 13 November 2008.
    All rights reserved.

    # vimeo.com/2299247 Uploaded 356 Plays 0 Comments

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