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Is there any refined experimental result on flux quantum?

  1. Feb 22, 2015 #1
    So far I have only found the initial papers of Deaver, Bascom; Fairbank, William and of Doll, R.; Näbauer, M.

    Is there any later and refined similar experiment result?
  2. jcsd
  3. Feb 23, 2015 #2


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    What do you mean by "experiments on flux quantum"?
    Do you mean experiments showing that flux is quantized? If so, see any paper/book on SQUIDs
  4. Feb 23, 2015 #3
  5. Feb 23, 2015 #4
    to: f95toli

    Deaver's results show poor stepwise distribution. Doll's results look systematic, but it is the only such result so far I have found.

    Deaver's data near the 1st step seem too big, while those around the 2nd and 3rd steps seem too small.
  6. Feb 23, 2015 #5
    I have read the "2e or Not 2e " article. It does not contain any new results, just story on Doll and Deaver's experiments.
  7. Feb 23, 2015 #6
    The magnetic flux quantum is a 2010 CODATA fundamental constant. As such it must have been measured with half-way reasonable accuracy (NIST states a relative standard uncertainty of 2.2e-8).

  8. Feb 23, 2015 #7


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    Could you please give some specific references. When I put those names into scholar I can only find references that are 40 years old. The flux quantum has -M Quack- has already pointed out been measured with very high accuracy in many more recent experiments. The inverse is the flux quantum (the Josephson constant) has been used to realize the de facto standard for the Volt for the past 20 years and is (after the second) the most precise realization of a SI unit we have (since it related the second to the volt).

    Also, I still don't understand what you are looking for? Precision measurements?
  9. Feb 24, 2015 #8
    First, thank f95toli and M Quack for providing the information.

    The specific references are:

    R. Doll and M. Nabauer, Phys. Rev. Lett. 7, 51 (1961); and
    B. S. Deaver and W. M. Fairbank, Phys. Rev. Lett. 7, 43 (1961).

    (In fact, in some articles they are cited in a "3 in 1" manner together with: N. Byers and C. N. Yang, Phys. Rev. Lett. 7, 46 (1961)).

    Of the NIST listing relating to flux quantum, the paper "Absolute determination of the magnetic flux quantum using superconducting magnetic levitation" looks promising, but I do not have access to the full text now. I will try later. But I doubt if they directly measured flux quantum, as Doll and Nabauer did. Specifically, if they simply measured the the Josephson constant and toke inverse of the latter as their flux quantum, it could be meaningless to physics topics like "is the flux quantum a fraction/multiple of hc/e?"
  10. Feb 24, 2015 #9
    I don't have full text access, but from the abstract it looks as if you might be right.


    "The current status of our superconducting magnetic levitation experiment for determining the magnetic flux quantum is described. The flux-up system has been improved significantly by using a Josephson voltage standard. Studies are also in progress to improve the mechanical measurement relevant to the floating body with the goal of reducing the uncertainty to less than 1 ppm"
  11. Feb 25, 2015 #10
    OK, I have just got some newest results of myself, according to which the flux is the combination of two terms:

    1) a quantized term some what greater than hc/(2e), (in fact the value of the factor has been determined; it is typically greater than one) and
    2) a varing term that depends on external field, the size of the coil, and the penetration depth.

    Depending on the direction of the external field, the varing term may decrease the overall flux, so when the external field is big enough and within a certain range, the measured flux can be close to hc/(2e). But as the external field further increases, the measured flux (step) decreases. This could be the reason why Deaver's data showed bigger 1st step and decreasing later steps.
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