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condensed-matter-physics.bigb
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= Condensed matter physics
{tag=Emergence}
{wiki}
= Condensed matter
{synonym}
<Condensed matter physics> is one of the best examples of <emergence>. We start with a bunch of small elements which we understand fully at the required level (<atoms>, <electrons>, <quantum mechanics>) but then there are complex properties that show up when we put a bunch of them together.
Includes fun things like:
* <superconductivity> and <superfluidity>
* <semiconductors>
As of 2020, this is the other "fundamental branch of physics" besides to <particle physics>/<nuclear physics>.
Condensed matter is basically <chemistry> but without reactions: you study a fixed state of matter, not a reaction in which compositions change with time.
Just like in chemistry, you end up getting some very well defined substance properties due to the incredibly large number of atoms.
Just like chemistry, the ultimate goal is to do de-novo <computational chemistry> to predict those properties.
And just like chemistry, what we can actually is actually very limited in part due to the exponential nature of <quantum mechanics>.
Also since chemistry involves reactions, chemistry puts a huge focus on liquids and solutions, which is the simplest state of matter to do reactions in.
Condensed matter however can put a lot more emphasis on solids than chemistry, notably because solids are what we generally want in end products, no one likes stuff leaking right?
But it also studies liquids, e.g. notably <superfluidity>.
One thing condensed matter is particularly obsessed with is the fascinating phenomena of <phase transition>.
\Video[https://www.youtube.com/watch?v=CY5V0q3K0zc]
{title=What Is <Condensed Matter Physics>? by Erica Calman}
{description=Cute. Overview of the main fields of physics research. Quick mention of his field, <quantum wells>, but not enough details.}
= Atomic, Molecular and Optical Physics
{parent=Condensed matter physics}
{wiki}
= AMO
{c}
{synonym}
{title2}
AMO is a slightly more general area than <condensed matter physics>, including related phenomena with smaller numbers atoms and optics. The two terms are however sometimes used as synonyms. The term AMO has gained wide usage and acceptability, see e.g.:
* https://www.sussex.ac.uk/amo/ at <University of Sussex>
If Ciro had had greater foresight, <when in doubt, choose the course that has the most experimental work>[this might have been what he studied at university]!
= Solid-state physics
{parent=Condensed matter physics}
{wiki}
= Solid-state
{synonym}
= Crystallography
{parent=Solid-state physics}
{wiki}
= Crystal system
{parent=Crystallography}
{wiki}
= Point group
{parent=Crystallography}
{wiki}
= Point groups in two dimensions
{parent=Point group}
{wiki}
= Point groups in three dimensions
{parent=Point group}
{wiki}
= Crystallographic restriction theorem
{parent=Point group}
{wiki}
= Bravais lattice
{c}
{parent=Crystallography}
{wiki}
= Crystal
{parent=Crystallography}
{wiki}
= Topological insulator
{parent=Solid-state physics}
{wiki}
Bibliography:
= Topology in condensed matter
{parent=Topological insulator}
{tag=GitHub book repo}
https://topocondmat.org/[]
Previously on <Edx>: https://www.edx.org/learn/quantum-physics-mechanics/delft-university-of-technology-topology-in-condensed-matter-tying-quantum-knots "DelftX: Topology in Condensed Matter: Tying Quantum Knots".
But then they regained their sanity and put the source code on <GitHub>: https://github.com/topocm/topocm_content and is <CC BY-SA>.
Uses an ungodly combination of <Jupyter> notebooks and <Pelican (static site generator)>.
= Electronic band theory
{parent=Condensed matter physics}
{wiki}
How are the bands measured experimentally?
Why are there gaps? Why aren't bands infinite? What determines the width of gaps?
Bibliography:
* <Applications of Quantum Mechanics by David Tong (2017)> Chapter 2 "Band Structure"
= Direct and indirect band gaps
{parent=Electronic band theory}
{wiki}
= Electrical resistivity and conductivity
{parent=Condensed matter physics}
{wiki}
= Resistivity
{synonym}
= Electrical reactance
{parent=Electrical resistivity and conductivity}
{wiki}
= Electrical impedance
{parent=Electrical reactance}
{wiki}
<Ciro Santilli> distinctly remembers being taught that at basic <electrical engineering> school during <Ciro Santilli's undergrad studies at the University of São Paulo>.
It really allows you to do <alternating current> calculations much as you'd do DC calculations with resistors, quite poweful. It must have been all the rage in the 1950s.
= Four-terminal sensing
{parent=Electrical resistivity and conductivity}
{wiki}
= Dependence of electrical resistivity on tempreature
{parent=Electrical resistivity and conductivity}
= Kondo effect
{c}
{parent=Dependence of electrical resistivity on tempreature}
{title2=Resistivity increase when temperature is lowered}
If you adda bit of impurities to certain materials, at low temperatures of a few <Kelvin> their <resistivity> actually starts increasing if you go below a certain critical temperature.
\Image[https://upload.wikimedia.org/wikipedia/commons/4/4a/Classickondo.png]
{title=<Kondo effect> graph for <gold> with added impurities}
= Semiconductor
{parent=Electrical resistivity and conductivity}
{wiki}
The basis of 1970-20XX <computers>, gotta understand them I guess?
= Doping
{disambiguate=Semiconductor}
{parent=Semiconductor}
= Type of semiconductor
{parent=Semiconductor}
= III-V semiconductor
{c}
{parent=Type of semiconductor}
Most notable example: <gallium arsenide>, see also: <gallium arsenide vs silicon>.
An important class of <semiconductors>, e.g. there is a dedicated III-V lab at: <École Polytechnique>: http://www.3-5lab.fr/contactus.php
= Superconductivity
{parent=Electrical resistivity and conductivity}
{tag=Second-order phase transition}
{wiki}
= Superconductor
{synonym}
= Superconducting
{synonym}
Experiments:
* "An introduction to superconductivity" by Alfred Leitner originally published in 1965, source: http://www.alfredleitner.com/
* Isotope effect on the critical temperature. http://hyperphysics.phy-astr.gsu.edu/hbase/Solids/coop.html mentions that:
\Q[If electrical conduction in mercury were purely electronic, there should be no dependence upon the nuclear masses. This dependence of the critical temperature for superconductivity upon isotopic mass was the first direct evidence for interaction between the electrons and the lattice. This supported the <BCS Theory> of lattice coupling of electron pairs.]
\Video[http://youtube.com/watch?v=O_zjGYvP4Ps]
{title=20. Fermi gases, BEC-BCS crossover by Wolfgang Ketterle (2014)}
{description=Part of the "Atomic and Optical Physics" series, uploaded by <MIT OpenCourseWare>.}
Actually goes into the equations.
Notably, https://youtu.be/O_zjGYvP4Ps?t=3278 describes extremely briefly an experimental setup that more directly observes pair condensation.
\Video[http://youtube.com/watch?v=Yx666k2XH8E]
{title=Superconductivity and Quantum Mechanics at the Macro-Scale - 1 of 2 by Steven Kivelson (2016)}
{description=For the Stanford Institute for Theoretical Physics. Gives a reasonable basis overview, but does not go into the meat of BCS it at the end.}
\Video[https://www.youtube.com/watch?v=bD2M7P6dTVA]
{title=The Map of <Superconductivity> by <#Domain of Science>}
{description=Lacking as usual, but this one is particularly good as the author used to work on the area as he mentions in the video.}
Lecture notes:
* https://austen.uk/courses/tqm/superconductivity/
Media:
* http://www.supraconductivite.fr/en/index.php#supra-explication
Cool CNRS video showing the condensed wave function, and mentioning that "every pair moves at the same speed". To change the speed of one pair, you need to change the speed of all others. That's why there's not energy loss.
Transition into superconductivity can be seen as a <phase transition>, which happens to be a <second-order phase transition>.
= Superconductor resistivity experiment video
{parent=Superconductivity}
https://andor.oxinst.com/learning/view/article/measuring-resistance-of-a-superconducting-sample-with-a-dry-cryostat Not a video, but well done, by <Oxford Instruments>.
\Video[https://www.youtube.com/watch?v=8gMKuy-gDQc]
{title=Superconductor, <Four-terminal sensing>[4-probe measurement] by Frederiksen Scientific A/S (2015)}
{description=OK experiment, illustrates the educational kit they sell. No temperature control, just dumps <liquid nitrogen> into conductor and watches it drop. But not too bad either. The kit sale link is broken (obviously, enterprise stuff), but there are no archives unfortunately. But it must be some <High-temperature superconductor>}
= Superconductor coil experiment video
{parent=Superconductivity}
{tag=Videos of all key physics experiments}
TODO!!! Even this is hard to find! A clean and minimal one! Why! All we can find are shittly levitating <YBCO> samples in <liquid nitrogen>! Maybe because <liquid helium> is expensive?
https://physics.stackexchange.com/questions/69222/how-can-i-put-a-permanent-current-into-a-superconducting-loop
\Video[https://www.youtube.com/watch?v=ba9zUW2Xf8Y]
{title=First 10T Tape Coil by Mark Benz}
{description=Dr. Mark Benz describes the first commercially sold superconducting magnet made by him and colleagues in 1965. The 10 Tesla magnet was made at GE Schenectady and they sold magnets to research facilities world wide before the team formed Intermagnetics General. IGC and Carl Rosner went on to pioneer MRI technology.}
= Superconductivity is a a form of superfluidity
{parent=Superconductivity}
We know that <superfluidity> happens more easily in <bosons>, and so electrons joins in <Cooper pairs> to form <bosons>, making a superfluid of <Cooper pairs>!
Isn't that awesome!
= Cooper pair
{c}
{parent=Superconductivity}
{wiki}
= Superconducting temperature
{parent=Superconductivity}
= Superconducting phase diagram
{tag=Phase transition}
{parent=Superconductivity}
There are various possibilities for the axes, but some common ones:
* temperature (T) vs magnetic field strength (B)
* temperature (T) vs proportion of each <chemical element> of a <binary alloy>
* temperature (T) vs pressure
\Image[https://upload.wikimedia.org/wikipedia/commons/5/51/Phase_diagram_superconductor_type_I.svg]
{title=Sketch of the typical <superconducting phase diagram> of a <Type-I superconductor>}
{disambiguate=Superconducting phase diagram}
\Image[https://upload.wikimedia.org/wikipedia/commons/thumb/6/6c/Superconductor_interactions_with_magnetic_field.png/425px-Superconductor_interactions_with_magnetic_field.png]
{title=Sketch of the typical <superconducting phase diagram> of a <Type-II superconductor>}
{disambiguate=Superconducting phase diagram}
= Type of superconductor
{parent=Superconductivity}
= Type-I superconductor
{parent=Type of superconductor}
{wiki}
\Image[https://upload.wikimedia.org/wikipedia/commons/5/51/Phase_diagram_superconductor_type_I.svg]
{title=Sketch of the typical <superconducting phase diagram> of a <Type-I superconductor>}
= Type-II superconductor
{parent=Type of superconductor}
{wiki}
\Image[https://upload.wikimedia.org/wikipedia/commons/thumb/6/6c/Superconductor_interactions_with_magnetic_field.png/425px-Superconductor_interactions_with_magnetic_field.png]
{title=Sketch of the typical <superconducting phase diagram> of a <Type-II superconductor>}
= High-temperature superconductivity
{parent=Type of superconductor}
{tag=1987 Nobel Prize in Physics}
{tag=Unsolved physics problem}
{title2=HTS}
{title2=1986}
{wiki}
= High-temperature superconductor
{synonym}
As of 2020, basically means "<liquid nitrogen> temperature", which is much cheaper than <liquid helium>.
The dream of course being <room temperature and pressure superconductor>.
\Image[https://upload.wikimedia.org/wikipedia/commons/b/bb/Timeline_of_Superconductivity_from_1900_to_2015.svg]
{height=600}
{title=Timeline of <superconductivity> from 1900 to 2015}
= Room temperature superconductor
{parent=High-temperature superconductivity}
{wiki}
= Resonating valence bond theory
{parent=Room temperature superconductor}
{wiki}
= Room temperature and pressure superconductor
{parent=Room temperature superconductor}
{wiki}
LK-99:
* https://www.tomshardware.com/news/superconductor-breakthrough-replicated-twice
= LK-99
{c}
{parent=Room temperature and pressure superconductor}
= List of High-temperature superconductors
{parent=High-temperature superconductivity}
{tag=Superconducting material}
= Yttrium barium copper oxide
{parent=List of High-temperature superconductors}
{tag=Barium compound}
{tag=Copper compound}
{wiki}
= YBCO
{c}
{synonym}
{title2}
Upside: superconducting above 92K, which is above the 77K of <liquid nitrogen>, and therefore much much cheaper to obtain and maintain than liquid helium.
Downside: it is brittle, so how do you make wires out of it? Still, can already be used in certain circuits, e.g. high temperature <SQUID devices>.
= Bismuth strontium calcium copper oxide
{parent=List of High-temperature superconductors}
{tag=Bismuth compound}
{tag=Copper compound}
{wiki}
= BSCCO
{c}
{synonym}
{title2}
Discovered in 1988, the first <high-temperature superconductivity>[high-temperature superconductor] which did not contain a rare-earth element.
= Superconducting material
{parent=Superconductivity}
= Applications of superconductivity
{parent=Superconductivity}
Superconductivity is one of the key advances of 21st century technology:
* produce powerful magnetic fields with <superconducting magnets>
* the <Josephson effect>, applications listed at: <applications of Josephson Junctions>{full}
Bibliography:
* https://en.wikipedia.org/wiki/Technological_applications_of_superconductivity
= Most important superconductor material
{parent=Applications of superconductivity}
As of 2023 the most important ones economicaly were:
* <Nb-Ti>: the most widely used one. Used e.g. to create the <magnetic fields> of the <Large Hadron Collider> Up to 15 <tesla (unit)>[T].
* <Nb-Sn>: more expensive than <Nb-Ti>, but can reach up to 30 <tesla (unit)>[T].
The main application is <magnetic resonance imaging>. Both of these are have to be <Liquid helium>, i.e. they are not "<high-temperature superconductor>" which is a pain. One big strength they have is that they are <metallic>, and therefore can made into wires, which is crucial to be able to make <electromagnetic coils> out of them.
= Superconductor I-V curve
{parent=Superconductivity}
TODO, come on, <Internet>!
Bibliography.
= Do superconductors carry infinite current?
{parent=Superconductor I-V curve}
No, see: <superconductor I-V curve>.
Bibliography:
* https://physics.stackexchange.com/questions/62664/how-can-ohms-law-be-correct-if-superconductors-have-0-resistivity on <Physics Stack Exchange>
* https://physics.stackexchange.com/questions/69222/how-can-i-put-a-permanent-current-into-a-superconducting-loop
* https://www.quora.com/Do-superconductors-produce-infinite-current-I-V-R-R-0-How-do-they-fit-into-quantum-theory
* https://www.reddit.com/r/askscience/comments/dcgdf/does_superconductivity_imply_infinite_current/
* https://www.reddit.com/r/askscience/comments/7xhb46/what_would_happen_if_a_voltage_was_applied_to_a/
\Video[https://www.youtube.com/watch?v=v8iD_waF_kM]
{title=Superconducting Short Circuits across Batteries by <Eugene Khutoryansky> (2020)}
{description=Well, internal battery resistance acts as the only resistor, and voltage drops to zero immediately outside of the battery. And you get a huge current.}
= BCS Theory
{c}
{parent=Superconductivity}
{tag=1972 Nobel Prize in Physics}
{title2=1957}
{wiki}
Main theory to explain Type I superconductors very successfully.
TODO can someone please just give the final predictions of BCS, and how they compare to experiments, first of all? Then derive them.
High level concepts:
* the wave functions of pairs of electrons (fermions) get together to form bosons. This is a <phase transition> effect, thus the specific sudden transition temperature.
* the pairs form a <Bose-Einstein condensate>
* once this new state is reached, all pairs are somehow entangled into one big wave function, and you so individual lattice imperfections can't move just one single electron off trajectory and make it lose energy
= Josephson effect
{c}
{parent=Superconductivity}
{title2=1962}
{tag=1973 Nobel Prize in Physics}
{wiki}
<Discrete> <quantum> effect observed in <superconductors> with a small insulating layer, a device known as a <Josephson junction>.
To understand the behaviour effect, it is important to look at the <Josephson equations> consider the following <Josephson effect regimes> separately:
* <DC Josephson effect>
* <AC Josephson effect>
* <Inverse AC Josephson effect>
A good summary from Wikipedia by physicist Andrew Whitaker:
\Q[at a junction of two superconductors, a current will flow even if there is no drop in voltage; that when there is a voltage drop, the current should oscillate at a frequency related to the drop in voltage; and that there is a dependence on any magnetic field]
Bibliography:
* https://www.youtube.com/watch?v=cnZ6exn2CkE "Superconductivity: Professor <Brian Josephson>". Several random excerpts from Cambridge people talking about the Josephson effect
= History of the Josephson effect
{parent=Josephson effect}
{tag=History of condensed matter physics}
{{wiki=Josephson_effect#History}}
In 1962 <Brian Josephson> published his inaugural paper predicting the effect as <Possible new effects in superconductive tunnelling>{full}.
In 1963 <Philip W. Anderson> and <John M. Rowell> published their paper that first observed the effect as <Possible new effects in superconductive tunnelling>{full}.
Some golden notes can be found at <True Genius: The Life and Science of John Bardeen> page 224 and around. <Philip W. Anderson> commented:
\Q[We were all - <Brian Josephson>[Josephson], Pippard and myself, as well as various other people who also habitually sat at the <Mond laboratory>[Mond] tea and participated in the discussions of the next few weeks - very much puzzled by the meaning of the fact that the <electric current>[current] depends on the <Josephson phase>[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."
= Possible new effects in superconductive tunnelling
{c}
{parent=History of the Josephson effect}
{tag=Physical Review Letters}
{title2=1963}
{title2=Prediction of the Josephson effect}
The inaugural that predicted the <Josephson effect>.
Published on <Physics Letters>, then a new journal, before they split into <Physics Letters A> and <Physics Letters B>. <True Genius: The Life and Science of John Bardeen> mentions that this choice was made rather than the more prestigious <Physical Review Letters> because they were not yet so confident about the results.
<Closed access academic journals are evil>[Paywalled] by <Elsevier> as of 2023 at: https://www.sciencedirect.com/science/article/abs/pii/0031916362913690
= Probable observation of the Josephson superconducting tunneling effect
{c}
{parent=History of the Josephson effect}
{tag=Physical Review Letters}
{title2=1963}
{title2=Observation of the Josephson effect}
Paper by <Philip W. Anderson> and <John M. Rowell> that first (?) experimentally observed the <Josephson effect>.
<Closed access academic journals are evil>[Paywalled] by the <American Physical Society> as of 2023 at: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.10.230
<DOI>: https://doi.org/10.1103/PhysRevLett.10.230
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.
\Image[https://raw.githubusercontent.com/cirosantilli/media/master/probable-observation-of-the-josephson-superconducting-tunneling-effect/1.png]
{title=Figure 1 of <Probable observation of the Josephson superconducting tunneling effect>}
{description=TODO what do the dotted lines mean?}
\Image[https://raw.githubusercontent.com/cirosantilli/media/master/probable-observation-of-the-josephson-superconducting-tunneling-effect/1.png]
{title=Figure 2 of <Probable observation of the Josephson superconducting tunneling effect>}
= Josephson effect regime
{c}
{parent=Josephson effect}
= DC Josephson effect
{c}
{parent=Josephson effect regime}
= AC Josephson effect
{c}
{parent=Josephson effect regime}
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 $V(t) = k$ a positive constant, then $\varphi$ just increases linearly without bound.
Therefore, from the first equation:
$$
I(t) = I_c \sin (\varphi (t))
$$
we see that the current will just vary sinusoidally between $\pm I_c$.
This meas that we can use a <josephson junction> as a perfect voltage to frequency converter.
Wikipedia mentions that this frequency is $484 GHz/mV$, 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.
An <I-V curve> can also be seen at: <image Electron microscope image of a Josephson junction its I-V curve>.
\Image[https://upload.wikimedia.org/wikipedia/commons/d/dd/I-V_characteristics_of_Josephson_Junction.JPG]
{title=<I-V curve> of the <AC Josephson effect>}
{description=
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 $\pm I_c$, 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[https://www.youtube.com/watch?v=FYnDcWFYyVA]
{title=Superconducting Transition of <Josephson Junction> by Christina Wicker (2016)}
{description=Amazing video that presumably shows the screen of a digital <oscilloscope> doing a voltage sweep as temperature is reduced and superconductivity is reached.}
\Image[https://upload.wikimedia.org/wikipedia/en/6/6b/STJ_IV_Curve.jpg?20110816180152]
{title=<I-V Curve> of a <superconducting tunnel junction>}
{description=So it appears that there is a zero current between $V=0$ and $V=2\Delta/e$. Why doesn't it show up on the <oscilloscope> sweeps, e.g. <video Superconducting Transition of Josephson Junction by Christina Wicker (2016}>?}
= Inverse AC Josephson effect
{parent=Josephson effect regime}
{{wiki=Josephson_effect#The_inverse_AC_Josephson_effect}}
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 preciesely? 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: https://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 https://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.
= Shapiro steps
{c}
{parent=Inverse AC Josephson effect}
= Josephson equations
{c}
{parent=Josephson effect}
{wiki}
Two equations derived <from first principles> by <Brian Josephson> that characterize the device, somewhat like an <I-V curve>:
$$
I(t) = I_c \sin (\varphi (t)) \\
\dv{\varphi(t)}{t} = \frac{2 e V(t)}{\hbar}
$$
where:
* $I_c$: <Josephson current>
* $\varphi$: the <Josephson phase>, a function $\R \to \R$ defined by the second equation plus initial conditions
* $V(t)$: input voltage of the system
* $I(t)$: current across the junction, determined by the input voltage
Note how these equations are not a typical <I-V curve>, as they are not an instantaneous dependency between voltage and current: the history of the voltage matters! Or in other words, the system has an internal state, represented by the <Josephson phase> at a given point in time.
To understand them better, it is important to look at some important cases separately:
* <AC Josephson effect>: V is a fixed <DC voltage>
= Josephson current
{c}
{parent=Josephson equations}
{title2=$I_c$}
{wiki}
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
{c}
{parent=Josephson equations}
{title2=$\varphi$}
{wiki}
A function $\R \to \R$ defined by the second of the <Josephson equations> plus initial conditions.
It represents an internal state of the junction.
= Josephson junction
{c}
{parent=Josephson effect}
{wiki}
A device that exhibits the <Josephson effect>.
\Image[https://web.archive.org/web/20220615163007im_/https://www.researchgate.net/publication/330223210/figure/fig9/AS:606819705688070@1521688500497/FIG-S2-Josephson-junction-of-a-second-sample-a-Scanning-electron-micrograph-of-sample.png]
{title=<Electron microscope> image of a <Josephson junction> its <I-V curve>}
{source=https://www.researchgate.net/figure/FIG-S2-Josephson-junction-of-a-second-sample-a-Scanning-electron-micrograph-of-sample_fig9_330223210}
= Pi Josephson junction
{c}
{parent=Josephson junction}
{wiki}
= Magnetic flux quantum
{parent=Josephson effect}
{tag=Physical Review Letters article}
{wiki}
TODO is there any relationship between this and the <Josephson effect>?
Experimental observation published as <Experimental Evidence for Quantized Flux in Superconducting Cylinders>.
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.
= Experimental Evidence for Quantized Flux in Superconducting Cylinders
{parent=Magnetic flux quantum}
{tag=Physical Review Letters article}
{title2=1961}
{title2=Bascom S. Deaver, Jr.}
{title2=William M. Fairbank}
Paywalled at: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.7.43
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:
\Q[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.
Dumping the fitures at: https://archive.org/details/experimental-evidence-for-quantized-flux-in-superconducting-cylinders One day we can also dump the paper scans when it goes into the public domain in 2056! <Public domain scientific paper by year>.
\Image[https://archive.org/download/experimental-evidence-for-quantized-flux-in-superconducting-cylinders-fig.-1/Experimental%20Evidence%20for%20Quantized%20Flux%20in%20Superconducting%20Cylinders%20Fig.%201.png]
{title=Figure 1 of <Experimental Evidence for Quantized Flux in Superconducting Cylinders>}
{description=The legend reads:
\Q[
(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.
]
}
\Image[https://archive.org/download/experimental-evidence-for-quantized-flux-in-superconducting-cylinders-fig.-1/Experimental%20Evidence%20for%20Quantized%20Flux%20in%20Superconducting%20Cylinders%20Fig.%202.png]
{title=Figure 2 of <Experimental Evidence for Quantized Flux in Superconducting Cylinders>}
{description=The legend reads:
\Q[
(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.
]
}
= Josephson constant
{c}
{parent=Magnetic flux quantum}
The inverse of the <magnetic flux quantum>.
= Symmetry breaking in superconductors
{parent=Josephson effect}
https://physics.stackexchange.com/questions/133780/superconductor-symmetry-breaking
As mentioned in <True Genius: The Life and Science of John Bardeen> page 224, the idea of <symmetry breaking> was a major motivation in Josephson's study of the <Josephson effect>.
= Applications of Josephson Junctions
{parent=Josephson effect}
* the basis for the most promising 2019 <quantum computing> implementation: <superconducting quantum computer>
* <Josephson voltage standard>: the most practical/precise <Volt> standard, which motivated the definition of the <ampere in the 2019 redefinition of the SI base units>
* <SQUID devices>, which are:
* very precise <magnetometer>
* the basis for <superconducting quantum computers>
= Josephson voltage standard
{c}
{parent=Applications of Josephson Junctions}
{wiki}
The most practical/precise volt standard.
It motivated the definition of the <ampere in the 2019 redefinition of the SI base units>
Quick <NIST> article about it: https://www.nist.gov/news-events/news/2013/04/primary-voltage-standard-whole-world (https://web.archive.org/web/20190410011041/https://www.nist.gov/news-events/news/2013/04/primary-voltage-standard-whole-world[archive])
The wiki page https://en.wikipedia.org/wiki/Josephson_voltage_standard contains amazing schematics of the device, apparently made by the <US government>.
\Image[https://upload.wikimedia.org/wikipedia/commons/2/2b/Layout_and_Schematic_of_JVS_Chip.jpg]
= SQUID device
{c}
{parent=Applications of Josephson Junctions}
{tag=Electronic component}
{tag=Magnetometer}
{wiki=SQUID}
Can be used as a very precise <magnetometer>.
There are high temperature <yttrium barium copper oxide> ones that work on <liquid nitrogen>.
\Video[https://www.youtube.com/watch?v=d_vrhzX3VcE]
{title=Superconducting Quantum Interference Device by Felipe Contipelli (2019)}
{description=Good intuiotionistic video. Some points deserved a bit more detail.}
\Video[https://www.youtube.com/watch?v=0kl3ucjh2Uw]
{title=Mishmash of SQUID interviews and talks by Bartek Glowaki}
{description=
The videos come from: https://www.ascg.msm.cam.ac.uk/lectures/[]. Vintage.
Mentions that the <SQUID device> is analogous to a <double-slit experiment>.
One of the segments is by John Clarke.
}
\Video[https://www.youtube.com/watch?v=ql2Yo5LgU8M]
{title=Superconducting Quantum Interference Devices by <UNSW> Physics (2020)}
{description=
An experimental lab video for <COVID-19> lockdown. Thanks, <COVID-19>. Presented by a cute and awkward Adam Stewart.
Uses a <SQUID device> and control system made by <STAR Cryoelectronics>. We can see <Mr. SQUID> EB-03 written on the probe and control box, that is their educational product.
As mentioned on the Mr. SQUID specs, it is a <high temperature superconductor>, so <liquid nitrogen> is used.
He then measures the <I-V curve> on an <Agilent Technologies oscilloscope>.
Unfortunately, the video doesn't explain very well what is happening behind the scenes, e.g. with a <circuit diagram>. That is the curse of university laboratory videos: some of them assume that students will have material from other internal sources.
* https://youtu.be/ql2Yo5LgU8M?t=211 shows the classic voltage oscillations, presumably on a magnetic field sweep, and then he puts a <magnet> next to the device from outside the <Dewar>
* https://youtu.be/ql2Yo5LgU8M?t=253 demonstrates the formation of <Shapiro steps>. Inserts a <Rohde & Schwarz> signal generator into the Dewar to vary the flux. The result is not amazing, but they are visible somewhat.
}
\Video[https://www.youtube.com/watch?v=7PJguB3Y8L8]
{title=The Ubiquitous <SQUID device>[SQUID] by John Clarke (2018)}
= DC SQUID
{parent=SQUID device}
{{wiki=SQUID#DC_SQUID}}
Two parallel <Josephson junctions>.
In <Ciro's ASCII art circuit diagram notation>:
``
|
+-+-+
| |
X X
| |
+-+-+
|
``
= Superconducting tunnel junction
{parent=Condensed matter physics}
{title2=STJ}
{wiki}
Specific type of <Josephson junction>. Probably can be made tiny and in huge numbers through <photolithography>.
\Image[https://web.archive.org/web/20210124093431im_/https://upload.wikimedia.org/wikipedia/commons/thumb/8/81/Superconducting_tunnel_junction.svg/735px-Superconducting_tunnel_junction.svg.png]
{title=Illustration of a thin-film superconducting tunnel junction (STJ)}
{description=The superconducting material is light blue, the insulating tunnel barrier is black, and the substrate is green.}
{source=https://upload.wikimedia.org/wikipedia/commons/8/81/Superconducting_tunnel_junction.svg}
\Video[http://youtube.com/watch?v=-HUVGWTfaSI]
{title=Quantum Transport, Lecture 14: Josephson effects by Sergey Frolov (2013)}
{description=https://youtu.be/-HUVGWTfaSI?t=878 mentions https://en.wikipedia.org/wiki/Electron-beam_lithography[maskless electron beam lithography] being used to produce STJs.}
= Superfluidity
{parent=Condensed matter physics}
{tag=Second-order phase transition}
{wiki}
= Superfluid
{synonym}
\Video[http://youtube.com/watch?v=7eZlF6IToQs]
{title=Alfred Leitner - Liquid Helium II the Superfluid by Alfred Leitner (1963)}
{description=Original source: http://www.alfredleitner.com[].}
\Video[http://youtube.com/watch?v=9FudzqfpLLs]
{title=Ben Miller experiments with superfluid helium by BBC (2011)}
{description=Just quickly shows the superfluid helium climbing out o the cup, no detailed setup. With https://www2.physics.ox.ac.uk/contacts/people/rtaylor[professor Robert Taylor] from the <University of Oxford>.}
= State of matter
{parent=Condensed matter physics}
{wiki}
= High pressure
{parent=State of matter}
{wiki}
\Video[https://www.youtube.com/watch?v=NqabT21d8VM]
{title=Something weird happens when you keep squeezing by Vox (2023)}
{description=<Sodium> becomes liquid when you compress it. Weird.}
= Solid
{parent=State of matter}
{wiki}
= Solid phase
{synonym}
= Liquid
{parent=State of matter}
{wiki}
= Liquid phase
{synonym}
= Gas
{c}
{parent=State of matter}
{wiki}
= Fermi gas
{c}
{parent=Gas}
{wiki}
= Electron gas
{parent=Fermi gas}
= Two-dimensional electron gas
{parent=Electron gas}
{wiki}
= 2DEG
{title2}
{synonym}
= Laughlin wavefunction
{c}
{parent=Two-dimensional electron gas}
{wiki}
= 1D Fermi gas
{c}
{parent=Fermi gas}
= Impenetrable Bose Gas
{parent=1D Fermi gas}
= Bose-Einstein condensate
{c}
{parent=State of matter}
{wiki=Bose–Einstein_condensate}
<Inward Bound by Abraham Pais (1988)> page 282 shows how this can be generalized from the <Maxwell-Boltzmann distribution>
= Materials science
{parent=Condensed matter physics}
{wiki}
= Type of material
{parent=Materials science}
= Glass
{parent=Type of material}
{wiki}
= Quantum dot
{parent=Type of material}
{wiki}
= Artificial quantum atom
{synonym}
{title2}
TODO WTF is this? How is it built? What is special about it?
Mentioned a lot in the context of <superconducting quantum computers>, e.g. https://youtu.be/t5nxusm_Umk?t=268 from <video Quantum Computing with Superconducting Qubits by Alexandre Blais (2012)>,
= Quantum dot single photon source
{parent=Quantum dot}
{wiki}
Mentioned at: <video Quantum Computing with Light by Quantum Light University of Sheffield (2015)> https://youtu.be/nyK-vhoOBpE?t=185[].
= Metal
{parent=Type of material}
{wiki}
= Metallic
{synonym}
= Alloy
{parent=Metal}
{wiki}
= Binary alloy
{parent=Alloy}
Bibliography: https://phys.libretexts.org/Bookshelves/Thermodynamics_and_Statistical_Mechanics/Heat_and_Thermodynamics_(Tatum)/17%3A_Chemical_Thermodynamics/17.09%3A_Binary_Alloys
= Metallurgy
{parent=Metal}
{wiki}
= Ingot
{parent=Metallurgy}
{wiki}
= Polymer
{parent=Type of material}
{wiki}
= Plastic
{parent=Polymer}
{wiki}
https://www.youtube.com/watch?v=PbuiIhr0LVA 7 Different Types of Plastic and Their Uses by Orange Plastics Academy (2018) Does not mention packaging foams.
= Material property
{parent=Materials science}
= Density
{parent=Material property}
{wiki}
= Magnet
{parent=Material property}
{wiki}
= Permanent magnet
{parent=Magnet}
= Curie temperature
{c}
{parent=Permanent magnet}
{tag=Phase transition}
{wiki}
\Image[https://web.archive.org/web/20231130040035im_/https://www.doitpoms.ac.uk/tlplib/ferromagnetic/images/FigureJ.gif]
{title=Variation of <saturation magnetisation> with temperature for Nickel}
{description=This graph shows what happens when you approach the <Curie temperature> from below.}
{source=https://www.doitpoms.ac.uk/tlplib/ferromagnetic/hysteresis.php}
= Ferromagnetism
{parent=Permanent magnet}
{tag=Second-order phase transition}
{wiki}
The wiki comments: https://en.wikipedia.org/w/index.php?title=Ferromagnetism&oldid=965600553#Explanation
\Q[The Bohr-van Leeuwen theorem, discovered in the 1910s, showed that classical physics theories are unable to account for any form of magnetism, including ferromagnetism. Magnetism is now regarded as a purely quantum mechanical effect. Ferromagnetism arises due to two effects from quantum mechanics: spin and the Pauli exclusion principle.]
= Magnetic hysteresis
{parent=Ferromagnetism}
{wiki}
To understand the graph, first learn/remember the difference between the <magnetic B and H field>.
The interest of the <magnetic hysteresis> graph is that it serves as an important characterization of a :
* its area gives you the hysteresis loss of the <transformer>, which is a major cause of efficiency loss of the component
* some key points of the curve give important characterizations of the core/material:
* <Saturation magnetisation>
* magnetization strength without field
* how much field you need to demagnetize it
This curve will also tell you how many turns of the coil will be needed to reach the required field.
\Image[https://upload.wikimedia.org/wikipedia/commons/thumb/c/c3/StonerWohlfarthMainLoop.svg/512px-StonerWohlfarthMainLoop.svg.png]
{title=Theoretical magnetic hysteresis plot}
{height=600}
\Video[https://www.youtube.com/watch?v=pXukVix5Pcw]
{title=Measurement of B-H characteristic}
{description=
1989. 1989 and they were making such awesome materials. It is hard to understand why university still exists given this.
Shows how you can obtain the <magnetic hysteresis> curve with an <AC source> plus an <oscilloscope in XY mode>. https://youtu.be/pXukVix5Pcw?t=193 clearly shows the measurement circuit.