Talk:Magnetic flux quantum

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Though the flux quantization was first discovered in superconductors, where current is carried by cooper pairs of charge 2e, the Aharonov-Bohm effect has been observed in many different, generally non-superconducting systems. The periodicity with the flux h/e in these systems is so general, that in many publications the flux quantum has been defined as \Phi_0 = \frac{h}{e} .

The definition mentioned in the article is therefore just one of two existing conventions and may lead to confusion if taken for granted. To avoid this confusion, it might be helpful if the article at least mentioned the existance of these two different conventions.

The difference between the Dirac flux quantum and the superconducting flux quantum should indeed be clarified, as both definitions unfortunately use the same formula symbol. If you want a separate page for the Dirac flux quantum, this one should be renamed accordingly. However, I think we can cover both definitions on one page, as they are closely related and the entry is hardly in danger of becoming bloated.

Also, where exactly does the quoted value come from? The CODATA 2002 recommended value is 2.067 833 72(81) x10^-15 Wb, see, e.g. Mohr and Taylor, Rev. Mod. Phys 177:1-107. The one given here may well be more up to date, but without an attributable source and an error estimate that's of little value.Tim Stadelmann 22:50, 5 April 2006 (UTC)

[edit] Plank constant

The article should expressly address the 2*pi*h-bar = h notations, using one consistentlyLeadSongDog (talk) 22:25, 26 November 2007 (UTC)

[edit] CGS versus SI Units

I think we need to check the formulae and make a clear demarcation between SI units and CGS units. CGS units include the c for the speed of light, whereas my understanding is that SI units omit the c and absorb it in the difference between Webers and Oersteds. If I substitute the accepted approximate values h = 6.626e-34, e = 1.602e-19, c=3e8 into the formulae,

\frac{h}{2 e} \simeq 2 \times 10^{-15} \frac{h c}{2 e} \simeq 6 \times 10^{-7}

The article states that the flux quantum is \simeq 2 \times 10^{-15} \mathrm{Wb}, so using the second formula for defining it is inconsistent and confusing.