In 1962 Brian Josephson published his inaugural paper predicting the effect as Section "Possible new effects in superconductive tunnelling".
Some golden notes can be found at True Genius: The Life and Science of John Bardeen page 224 and around. Philip W. Anderson commented:
We were all - Josephson, Pippard and myself, as well as various other people who also habitually sat at the Mond tea and participated in the discussions of the next few weeks - very much puzzled by the meaning of the fact that the current depends on the phase
As part of the course Anderson had introduced the concept of broken symmetry in superconductors. Josephson "was fascinated by the idea of broken symmetry, and wondered whether there could be any way of observing it experimentally."
Paper by Philip W. Anderson and John M. Rowell that first (?) experimentally observed the Josephson effect.
TODO understand the graphs in detail.
They used tin-oxide-lead tunnel at 1.5 K. TODO oxide of what? Why two different metals? They say that both films are 200 nm thick, so maybe it is:
   -----+------+------+-----
...  Sn | SnO2 | PbO2 | Pb  ...
   -----+------+------------
          100nm 100nm
A reconstruction of their circuit in Ciro's ASCII art circuit diagram notation TODO:
DC---R_10---X---G
There are not details of the physical construction of course. Reproducibility lol.
Figure 1.
Figure 1 of Probable observation of the Josephson superconducting tunneling effect
. TODO what do the dotted lines mean?
Figure 2.
Figure 2 of Probable observation of the Josephson superconducting tunneling effect
.
AC Josephson effect by Ciro Santilli 37 Updated 2025-07-16
This is what happens when you apply a DC voltage across a Josephson junction.
It is called "AC effect" because when we apply a DC voltage, it produces an alternating current on the device.
By looking at the Josephson equations, we see that a positive constant, then just increases linearly without bound.
Therefore, from the first equation:
we see that the current will just vary sinusoidally between .
This meas that we can use a Josephson junction as a perfect voltage to frequency converter.
Wikipedia mentions that this frequency is , so it is very very high, so we are not able to view individual points of the sine curve separately with our instruments.
Also it is likely not going to be very useful for many practical applications in this mode.
Figure 1.
I-V curve of the AC Josephson effect
. Source.
Voltage is horizontal, current vertical. The vertical bar in the middle is the effect of interest: the current is going up and down very quickly between , the Josephson current of the device. Because it is too quick for the oscilloscope, we just see a solid vertical bar.
The non vertical curves at right and left are just other effects we are not interested in.
TODO what does it mean that there is no line at all near the central vertical line? What happens at those voltages?
Video 1.
Superconducting Transition of Josephson junction by Christina Wicker (2016)
Source. Amazing video that presumably shows the screen of a digital oscilloscope doing a voltage sweep as temperature is reduced and superconductivity is reached.
Figure 2.
I-V curve of a superconducting tunnel junction
. So it appears that there is a zero current between and . Why doesn't it show up on the oscilloscope sweeps, e.g. Video 1. "Superconducting Transition of Josephson junction by Christina Wicker (2016)"?
If you shine microwave radiation on a Josephson junction, it produces a fixed average voltage that depends only on the frequency of the microwave. TODO how is that done more precisely? How to you produce and inject microwaves into the thing?
It acts therefore as a perfect frequency to voltage converter.
The Wiki page gives the formula: en.wikipedia.org/wiki/Josephson_effect#The_inverse_AC_Josephson_effect You get several sinusoidal harmonics, so the output is not a perfect sine. But the infinite sum of the harmonics has a fixed average voltage value.
And en.wikipedia.org/wiki/Josephson_voltage_standard#Josephson_effect mentions that the effect is independent of the junction material, physical dimension or temperature.
All of the above, compounded with the fact that we are able to generate microwaves with extremely precise frequency with an atomic clock, makes this phenomenon perfect as a Volt standard, the Josephson voltage standard.
TODO understand how/why it works better.
Josephson current by Ciro Santilli 37 Updated 2025-07-16
Maximum current that can flow across a Josephson junction, as can be directly seen from the Josephson equations.
Is a fixed characteristic value of the physical construction of the junction.
Josephson phase by Ciro Santilli 37 Updated 2025-07-16
A function defined by the second of the Josephson equations plus initial conditions.
It represents an internal state of the junction.
Josephson junction by Ciro Santilli 37 Updated 2025-07-16
A device that exhibits the Josephson effect.
Figure 1.
Electron microscope image of a Josephson junction its I-V curve
. Source.
Magnetic flux quantum by Ciro Santilli 37 Updated 2025-07-16
TODO is there any relationship between this and the Josephson effect?
This appears to happen to any superconducting loop, because the superconducting wave function has to be continuous.
Video "Superconducting Qubit by NTT SCL (2015)" suggests that anything in between gets cancelled out by a superposition of current in both directions.
The first published experimental observation of the magnetic flux quantum.
The paper that follows it in the journal is also of interest, "Theoretical Considerations Concerning Quantized Magnetic Flux In Superconducting Cylinders" by N. Byers and C. N. Yang, it starts:
In a recent experiment, the magnetic flux through a superconducting ring has been found to be quantized in units of ch/2e. Quantization in twice this unit has been briefly discussed by London' and by Onsager. ' Onsager' has also considered the possibility of quantization in units ch/2e due to pairs of electrons forming quasi-bosons.
So there was some previous confusion about the flux quantum due to the presence of Cooper pairs or not.
Figure 1.
Figure 1 of Experimental Evidence for Quantized Flux in Superconducting Cylinders
. The legend reads:
(Upper) Trapped flux in cylinder No. 1 as a function of magnetic field in which the cylinder was cooled below the superconducting transition. temperature. The open circles are individual data points. The solid circles represent th, e average value of all data points at a particular value of applied field including all the points plotted and additional data which could not be plotted due to severe overlapping of points. Approximately two hundred data points are represented. The lines are drawn at multiples of hc/2e.
(Lower) Net flux in cylinder No. 1 before turning off the applied field in which it was cooled as a function of the applied field. Open and solid circles have the same significance as above. The lower line is the diamagnetic calibration to which all runs have been normalized. The other lines are translated vertically by successive steps of hc/2e.
Figure 2.
Figure 2 of Experimental Evidence for Quantized Flux in Superconducting Cylinders
. The legend reads:
(Upper) Trapped flux in cylinder No. 2 as a function of magnetic field in which the cylinder was cooled below the superconducting transition temperature. The circles and triangles indicate points for oppositely directed applied fields. Lines are drawn at multiples of hc/2e.
(Lower) Net flux in cylinder No. 2 before turning off the applied field as a function of the applied field. The circles and triangles are points for oppositely directed applied fields. The lower line is the diamagnetic calibration to which all runs have The other been normalized. lines are translated vertically by successive steps of hc/2e.
The most practical/precise volt standard.
The wiki page en.wikipedia.org/wiki/Josephson_voltage_standard contains amazing schematics of the device, apparently made by the US Government.
Figure 1.
Schematic of a typical Josephson voltage standard chip
. Source.
Figure 2.
Sam Benz demonstrating the equipment required the voltage standard
. Source.
Video 1.
The evolution of voltage metrology to the latest generation of JVSs by Alain Rüfenacht
. Source. Talk given in 2023. The speaker is from NIST, and the talk was hosted by the BIPM. Fantastic talk.
Video 2.
Technical aspects of realizing the DC volt in the laboratory with a JVS by Stéphane Solve
. Source. Talk given in 2023. The speaker is from BIPM, and the talk was hosted by the BIPM. Fantastic talk.
Specific type of Josephson junction. Probably can be made tiny and in huge numbers through photolithography.
Figure 1. Source. The superconducting material is light blue, the insulating tunnel barrier is black, and the substrate is green.
Video 1.
Quantum Transport, Lecture 14: Josephson effects by Sergey Frolov (2013)
Source. youtu.be/-HUVGWTfaSI?t=878 mentions maskless electron beam lithography being used to produce STJs.
Superfluidity by Ciro Santilli 37 Updated 2025-07-16
Video 1.
Alfred Leitner - Liquid Helium II the Superfluid by Alfred Leitner (1963)
Source. Original source: www.alfredleitner.com.
Video 2.
Ben Miller experiments with superfluid helium by BBC (2011)
Source. Just quickly shows the superfluid helium climbing out o the cup, no detailed setup. With professor Robert Taylor from the University of Oxford.
High pressure by Ciro Santilli 37 Updated 2025-07-16
Video 1.
Something weird happens when you keep squeezing by Vox (2023)
. Source. Sodium becomes liquid when you compress it. Weird.

Pinned article: Introduction to the OurBigBook Project

Welcome to the OurBigBook Project! Our goal is to create the perfect publishing platform for STEM subjects, and get university-level students to write the best free STEM tutorials ever.
Everyone is welcome to create an account and play with the site: ourbigbook.com/go/register. We belive that students themselves can write amazing tutorials, but teachers are welcome too. You can write about anything you want, it doesn't have to be STEM or even educational. Silly test content is very welcome and you won't be penalized in any way. Just keep it legal!
We have two killer features:
  1. topics: topics group articles by different users with the same title, e.g. here is the topic for the "Fundamental Theorem of Calculus" ourbigbook.com/go/topic/fundamental-theorem-of-calculus
    Articles of different users are sorted by upvote within each article page. This feature is a bit like:
    • a Wikipedia where each user can have their own version of each article
    • a Q&A website like Stack Overflow, where multiple people can give their views on a given topic, and the best ones are sorted by upvote. Except you don't need to wait for someone to ask first, and any topic goes, no matter how narrow or broad
    This feature makes it possible for readers to find better explanations of any topic created by other writers. And it allows writers to create an explanation in a place that readers might actually find it.
    Figure 1.
    Screenshot of the "Derivative" topic page
    . View it live at: ourbigbook.com/go/topic/derivative
  2. local editing: you can store all your personal knowledge base content locally in a plaintext markup format that can be edited locally and published either:
    This way you can be sure that even if OurBigBook.com were to go down one day (which we have no plans to do as it is quite cheap to host!), your content will still be perfectly readable as a static site.
    Figure 2.
    You can publish local OurBigBook lightweight markup files to either https://OurBigBook.com or as a static website
    .
    Figure 3.
    Visual Studio Code extension installation
    .
    Figure 4.
    Visual Studio Code extension tree navigation
    .
    Figure 5.
    Web editor
    . You can also edit articles on the Web editor without installing anything locally.
    Video 3.
    Edit locally and publish demo
    . Source. This shows editing OurBigBook Markup and publishing it using the Visual Studio Code extension.
    Video 4.
    OurBigBook Visual Studio Code extension editing and navigation demo
    . Source.
  3. https://raw.githubusercontent.com/ourbigbook/ourbigbook-media/master/feature/x/hilbert-space-arrow.png
  4. Infinitely deep tables of contents:
    Figure 6.
    Dynamic article tree with infinitely deep table of contents
    .
    Descendant pages can also show up as toplevel e.g.: ourbigbook.com/cirosantilli/chordate-subclade
All our software is open source and hosted at: github.com/ourbigbook/ourbigbook
Further documentation can be found at: docs.ourbigbook.com
Feel free to reach our to us for any help or suggestions: docs.ourbigbook.com/#contact