Talk:Josephson effect

Practical uses and Nobel Prize worthiness
There isn't a single word about practical uses or its generic significance to further advancing physics. I mean Nobel prizes are awarded for achievements beneficial to the mankind, abstract beauty is not enough. — Preceding unsigned comment added by 195.70.48.245 (talk) 11:28, 10 December 2004 (UTC)


 * Maybe his psychic quantum theory powers affected the judges enough to nominate him? — Preceding unsigned comment added by 65.2.114.221 (talk) 02:39, 7 March 2005 (UTC)


 * I'd have to agree; the article should mention why this was considered Nobel-worthy. --Starwed 10:42, 5 May 2007 (UTC)
 * I can't believe it!! Re practical uses, you don't seem to have read the section 'Applications'. --Brian Josephson (talk) 16:18, 14 February 2023 (UTC)
 * When that comment was written, more than 15 years ago, there was no 'Applications' section. MrOllie (talk) 15:42, 13 March 2023 (UTC)
 * Fair enough. That bit sprung right to my eyes when I checked a recent update. Brian Josephson (talk) 17:41, 13 March 2023 (UTC)

Uses ?
There is nothing about what all this means! I mean, it explains the technical parts, gives the proof, shows the equation- all of which is well and good, but I came beause I heard it was being used in ultra-fast chip prototypes and other interesting devices, and the page gives me nada. -- maru


 * I think the writer could only benefit from understanding the physical principles behind the Josephson effect, before engaging in the trivia of applications, which sadly risk becoming nothing but a mindless tabulation of data, without the deeper understanding, which lately seems to have become a dirty word. Certainly the applications are humanly and economically very important, but please spare us from having the applications promoted and discussed by fast Eddy, and other busybodies who are too eager to talk about some reality using a few memorized buzzwords, but are incapable of doing anything useful with that reality. — Preceding unsigned comment added by 24.81.112.177 (talk) 10:12, 12 October 2005 (UTC)


 * I have no real problem with the principles and the explanations; however, in the end all research should come back to pratical applications- science is a tool, not an art. And I have no idea what most of your comment is talk about. --maru (talk) Contribs 18:16, 21 January 2006 (UTC)


 * I got into this for reasons that can be seen from the Anderson-Rowell section of this talk page. Apart from correcting a misspelling of my name I'll leave the article untouched, but comment that the statement of what I discovered seems to me unhelpful, and unless one is going to go into great detail talking about phases etc. (which would merit a section its own) the best thing would simply be to indicate that 1962 was the date when the predictions were made.  I'd also like to add that theoreticians would strongly dispute the suggestion that research in physics is only of interest in terms of practical applications.  That would among other things rule out astronomy, whose practical relevance stopped as soon as the positions of the sun and moon were figured out.  That isn't of course to belittle the importance of discussing the practical applications and including them in the article. --Brian Josephson (talk) 16:31, 16 May 2012 (UTC)
 * Science is in the first place is the search for knowledge. Practical applications are a useful extra when they exist.  Particle physics is another matter having become speculation, rather than clear knowledge or unambigous understanding. Brian Josephson (talk) 16:27, 14 February 2023 (UTC)


 * There is another entry,  Josephson Junction, which describes a bit the applications. Maybe the content of these two articles coulb be merged in the future?  — Preceding unsigned comment added by Filou (talk • contribs) 16:46, 20 January 2006 (UTC)


 * That seems like a good idea to me; the effect seems to be more embracing than the junction, so I would merge in Junction to Effect. --maru (talk) Contribs 18:16, 21 January 2006 (UTC)

entries merged
The content of the page Josephson junction has been merged into the page describing the Josephson effect, and a few words about applications have been added. All this can still be improved, feel free to do it. Filou 22:21, 23 January 2006 (UTC)

Correction
Added a correction: the Josephson effect does not define the SI volt, it is presently used as a representation for the volt (there is a relative uncertainty of 4 x 10^-7 of the voltage generated by the Josephson effect to the SI volt.) Dalle 19:55, 15 March 2006 (UTC)


 * Looks to me like it is: Volt Confuted 01:58, 19 January 2007 (UTC)

Temperature unit
I changed Kelvin to kelvin, to follow proper SI practice in English. — Preceding unsigned comment added by 153.9.92.145 (talk) 17:47, 1 May 2006 (UTC)

I-V characteristic
I am working with Josephson junction every day, but I never saw such a strange I-V characteristic. Can this be substituted to something standard like tunnel JJ IVC or RSJ IVC? — Preceding unsigned comment added by E goldobin (talk • contribs) 17:44, 21 November 2006 (UTC)

Historical question
The Biography for Josephson says that he discovered the Josephson effect. The introduction for the Josephson effect (this article) says that he predicted it. Which is correct? This discrepancy should be addressed. — Preceding unsigned comment added by 140.180.7.193 (talk) 09:17, 29 November 2006 (UTC)


 * This bothered me too, but I imagine it's sloppy language; predicting an effect can be thought of discovering it's possibility in a theory. But even if that's what was meant, it certainly gives the wrong impression.  --Starwed 10:40, 5 May 2007 (UTC)

Practical uses and follow-up
In earlier versions, the article contained more links and comments about practical issues. Why they vanished is unclear to me ... Filou 22:11, 4 September 2007 (UTC)

'The Josephson effect is the phenomenon of current flow across two weakly...' shouldn't this be more specific current of cooper pairs, so not quasi particles?--129.125.6.1 (talk) 10:32, 4 December 2008 (UTC)

Consistency in Equations
Is the proper constant in the equations $$\displaystyle \frac{\hbar}{2e}$$ or $$\displaystyle \frac{h}{2e}$$? $$h$$ and $$\hbar$$ differ by a factor of $$2\pi$$; this article uses them interchangably. Confuted 01:59, 19 January 2007 (UTC)
 * In its current state, the article uses $$h$$ only when giving the frequency. This is correct.  The angular frequency (e.g. rad/s) is $$\frac{2 e}{\hbar}\cdot U_{DC}$$, but the frequency (e.g. 1/s) is $$\frac{2 e}{h}\cdot U_{DC}$$.  -Beastinwith (talk) 17:22, 5 August 2008 (UTC)

I wonder if you want to leave the reader with that confusion or at least uncertainty on the mixed use of $$h$$ and $$\hbar$$ in this article? For the sake of clarity, please use one or the other, but not both.

Reddwarf2956 (talk) 00:32, 23 August 2009 (UTC)

Any other process Apjdiehard98 (talk) 18:14, 4 January 2017 (UTC)

Clarification
My impression from reading other sources is that a current must be induced in the case of the DC Josephson effect. The special thing is that the current then flows across the barrier without a voltage drop. If this is accurate I think it should be mentioned in the description of the DC Josephson effect. -Beastinwith (talk) 03:42, 5 August 2008 (UTC)

Physical Intuition
This entry contains little in the way of physical interpretations of the Josephson effects. If anybody has some physical intuition beyond the listed equations I think that including it would improve the article. -Beastinwith (talk) 03:42, 5 August 2008 (UTC)
 * the effect also occurs in superfluids. http://en.wikipedia.org/wiki/Quantum_gyroscope http://www.innovations-report.com/html/reports/physics_astronomy/report-39604.html. just-emery (talk) 12:56, 8 May 2009 (UTC)
 * clearly the thing that ties all these things together and that forms the basis of superconductivity and I presume superfluidity as well is 'cooper pairs' (and/or 'lone pairs'). readers that want to dig deeper into this phenomenon should probably be directed there. just-emery (talk) 13:28, 8 May 2009 (UTC)


 * According to the article Superfluid:
 * "Superfluid acts as if it were a mixture of a normal component, with all the properties associated with normal fluid, and a superfluid component."
 * I assume that the same is true for superconductors. If so then the nonsuperconducting component would be responsible for the voltage drop while the superconducting component would be responsible for the ac current. just-emery (talk) 23:52, 3 July 2009 (UTC)

ac josephson current/energy loss
the ac current must radiate energy so how is it replenished? just-emery (talk) 12:35, 8 May 2009 (UTC)
 * From the source that supplies the dc voltage. --Brian Josephson (talk) 16:36, 16 May 2012 (UTC)

t
Is t in the equations the time or the thickness. At this point I think it is the time, but before reading below I interpreted it as the thickness of the gap. Would someone please state which it is? David R. Ingham (talk) 22:02, 20 January 2012 (UTC)


 * t is time Tls60 (talk) 22:42, 20 January 2012 (UTC)

Anderson-Rowell reference
Following comment by Anderson, who may have looked in the reference list at the end and found that his paper with Rowell announcing the first experimental observation of the effect was not included, I've made the in-text reference a proper reference (is it only subjects like cold fusion that the w'pedia vigilantes give their undivided attention to?). I merely transferred the details that were there, and maybe someone with the time to spare can (a) check the reference is correct (b) include the title of the paper (c) include a suitable link, doi or whatever.--Brian Josephson (talk) 11:02, 16 May 2012 (UTC)

Update: ignore the above request: I found I had the title ready to hand, and it is all fixed now! --Brian Josephson --Brian Josephson (talk) 16:10, 16 May 2012 (UTC)

I've learned that it was Anderson himself who put in the key reference. At his advanced age he can perhaps be excused for not doing it in the officially authorised way! --Brian Josephson (talk) 08:08, 17 May 2012 (UTC)

magnetic field sensitivity
The article lists 3 main effects (DC/AC/inverse AC), but the magnetic field sensitivity is equally important and should be included in the list, with a suitable accompanying graphic. --Brian Josephson (talk) 08:07, 17 May 2012 (UTC)

Request to Brian Josephson
Could Brian Josephson make his article containing the prediction of the effect openly/freely available (as a link) to all readers of the Josephson effect article in Wikipedia?--86.120.44.145 (talk) 17:57, 20 May 2012 (UTC)
 * My Nobel lecture is already linked in to the WP article. Was there another article you had in mind (I did do one for a book but can't track it down, but if you have the details that could help my search).--Brian Josephson (talk) 13:39, 13 October 2019 (UTC)

I.M. Yurin's Theory
I'm removing the paragraph that links the article by "I.M. Yurin". The article in question, while it is in a peer-reviewed journal, has not been cited elsewhere, and does not seem to be notable enough to warrant inclusion. The author does not appear to be associated with a notable university or research institution, and I suspect that the article author himself is the one posting this information. If the editor chooses to restore the link without commenting on this page, I will refer the matter for dispute resolution, as he has already engaged in the same behavior on the BCS theory page. PianoDan (talk) 20:13, 20 November 2012 (UTC)

merge/add Josephson energy into Josephson effect
I'm proposing a merge from the Josephson energy article, which seems to cover a fair amount of the same ground as this one, with additional math. If the two articles should be separate, the Josephson energy article needs to be cleaned up and have references added. I'm not familiar enough with the topic to tell if there should be separate articles or not, but it looks like this is the more comprehensive article. -- phoebe / (talk to me) 04:36, 2 January 2013 (UTC)
 * Yes, at this point the merge would be beneficial for both articles (and yes, I am familiar with the topic). In principle, I can imagine a separate article on Josephson energy, but this requires a fair amount of work to create it. What is it there now is best to be merged.--Ymblanter (talk) 06:53, 2 January 2013 (UTC)

I think that merging is a good idea. — Preceding unsigned comment added by 84.130.188.188 (talk • contribs) 02:28, 28 January 2014 (UTC)
 * I also agree that merging would be a sound idea as it would help people better understand Graphene. Prehaps, you could merge it an just make Josephson Energy a separate section of the Josephson effect article. Physics16 (talk) 01:01, 16 April 2014 (UTC)


 * I have performed the merge. Should the very short Josephson phase and Josephson penetration depth be merged as well? Antony–22 (talk⁄contribs) 19:06, 22 April 2016 (UTC)

What does the critical current depend on
Article says "The critical current is an important phenomenological parameter of the device that can be affected by temperature as well as by an applied magnetic field." [How] Does it depend on the materials and dimensions of the device ? (other articles talk of a critical current density) - Rod57 (talk) 04:58, 23 December 2015 (UTC)
 * It is inversely proportional to the normal state resistance, which takes care of the device properties.--Ymblanter (talk) 07:01, 23 December 2015 (UTC)

Voltage-to-curvature conversion claim
Can somebody provide a good reference for the voltage-to-curvature converter claim? I am just a layman in the fields of both QM and GR, but the claim that a Josephson junction can be used to electronically modulate spacetime curvature seems suspect to me - wouldn't that be a huge leap in our current understanding? The only source I can find for it is this arXiv article and it's by the same author that added the section to this Wikipedia page. Peter Kazakoff (talk) 20:37, 28 July 2017 (UTC)
 * This claim looks highly doubtful. I've done this quick calculation according to the suggested formula and Einstein field equations: $$ R = (4/3)(48 m^{*} e U/\hbar^2) = (8 \pi G/c^4) T $$, where m* was taken as double the electron mass. The effective mass density is $$\rho = T/c^2 = U \cdot (9.0 \times 10^{46} \text{kg}/\text{m}^3/\text{V})$$. For a typical junction voltage of 1 mV and junction volume of 1 &mu;m3 (see, e.g. Josephson voltage standard), this results in density of 9.0e+43 kg/m3 and total mass of 9.0e+25 kg, which is 15 times the mass of Earth. Unless I misunderstood the implied phenomenon, the resultant gravitational field would definitely destroy our planet, which obviously does not happen. Should this section be removed? Pakras (talk) 10:24, 13 September 2017 (UTC)
 * Since this seems physically unreasonable, because there is no good citation for it, and because it was posted by the author of the obscure paper it came from, I have decided to be bold and remove it for the time being. Peter Kazakoff (talk) 16:24, 18 October 2017 (UTC)

Value of e
The section "Josephson equations" uses the constant $e$ in several places. What this means is not defined in the text. In some places it's raised to a power, which makes me think it's the base of natural logarithms. But the context is electrodynamics, making me think it might be the elementary charge. Which is it? If it's one or the other in different contexts, we should distinguish the latter by using $qe$ instead. Hairy Dude (talk) 18:36, 11 May 2022 (UTC)
 * e which is raised to a power is a number, all other e's in this section stand for electron charge.--Ymblanter (talk) 18:40, 11 May 2022 (UTC)
 * I think people knowledgeable enough about physics to be able to appreciate the equations won't have any problem knowing which version of $e$ applies in each case, whereas your proposed alternative will only tend to cause confusion. However, at the start where it says 'If the electric potential difference across the junction is $V$', one might include for clarity the fact that $e$ denotes the charge on the electron. --Brian Josephson (talk) 18:54, 11 May 2022 (UTC)

Problem on demonstration of $I(t) = I_c \sin (\varphi (t)) $
By definition, I(t) is proportionnal to the derivative of $\dot n_A$.

So, $I_c$ is proportionnal to $\frac{2K\sqrt{n_An_B}}{\hbar}$. In case of V nul, the DC Josephson effect gives us a constant current $\dot n_A$. However, according to the formula $\dot n_A=\frac{2K\sqrt{n_An_B}}{\hbar}\sin \varphi$, $\dot n_A$ is proportional to $ n_A$  which is a first order differential equation and so it is not constant.

If someone could add an explanation of that. AnthonyB20 (talk) 22:31, 8 November 2022 (UTC)
 * I don't think much of that section of the web page, based on Feynman's oversimplification but pretty incomprehensible as presented. The original proof was only two pages! But perhaps the whole section should be removed, with a reference somewhere to the original calculation in Physics Letters. --Brian Josephson (talk) 18:01, 9 November 2022 (UTC)

Nothing on Amplifiers?
Probably the most common use right now, and I see no reference to it. A bit srange, maybe I am missing something. 2600:4040:9AE7:B400:9878:B6B9:D4E8:57CC (talk) 17:23, 12 January 2023 (UTC)