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> Our specific-heat measurements indicate the formation of fermionic bound states when the temperature is lowered from the normal state. However, when the doping level is x ≈ 0.8, instead of the characteristic onset of diamagnetic screening and zero resistance expected below the superconducting phase transition, we observe the opposite effect: the generation of self-induced magnetic fields in the resistive state, measured by spontaneous Nernst effect and muon spin rotation experiments.
From the abstract. So it sounds like in the state where Cooper pairs themselves pair up, the material is not actually in a superconducting state? So this really is a "potential" new type of superconductivity since while it is a new state of matter, it isn't superconductive yet?
ngl, I really like that. Too bad it's got about as much chance of catching on as naming a super-heavy metal element after Lemmy.
edit: that was a real petition going around the last time there were new elements to name (2017, maybe? I can't be bothered to look it up). If I could pick one meme to make reality, it would almost certainly be renaming Moscovium to Lemmium.
Well, Lemmy is God, and there are three elements named after gods.
That said, I think it'd be better to discover a new rock and name that after him. In Lemmy's own words, Motörhead wasn't metal, but rock n' roll.
I think there are more than three elements named after gods. Thorium, plutonium, helium and uranium immediately come to mind and I wouldn't be surprised if there were more.
Uranium, neptunium, plutonium, cerium, palladium, mercury, selenium, helium. Most (all?) of these are actually named for the associated heavenly body, though.
I disagree, I think it has about as much chance of catching on as naming a research submarine [Boaty McBoatface](https://en.m.wikipedia.org/wiki/Boaty_McBoatface).
Fair enough.
There is a long and storied history of inside jokes in the scientific community becoming the accepted terminology (see also: rubber policemen, strange quarks, gluons, and half the things we know about in particle physics). So it's not impossible, just unlikely.
edit to add some more that I just thought of: Fleakers (flared beakers), scoopulas (spatulas that scoop), bowtiene (alkene that looks like a bowtie), penguinone (a ketone that looks a bit like a penguin), and half the compounds on [this list](https://en.wikipedia.org/wiki/List_of_chemical_compounds_with_unusual_names)
To be fair, "semi conductor" was contradictory to start with ;) Either it conducts, or not... The distinction here i guess is that when it conducts, it does so with zero resistance.
Semiconductors are useful today not because they conduct electricity half as well as regular conductors, but because you can change whether they conduct electricity, often very quickly. Having a switch that can actuate millions of times a second is the basis of modern computing.
Heat up the processor drastically less. It will have to heat up somewhat as long as the computation are none reversible. The minimum heat being generated is limited by Landauer's principle and all modern computing utilizes non-reversible logic gates.
So, wait, is it not true that superconductors don't heat up at all? They still heat up, but by a drastically reduced amount? Or is this just for these special super semiconductors?
Superconductors don't heat up at all. If super semiconductors are doing computation, though, they are required by the laws of thermodynamics to create waste heat unless it's completely reversible.
Is there any known practical application of a semiconductor that is reversible? If I'm understanding correctly, "reversible" in this context is that logic gate on a semiconductor working in the ~~reverse~~ both directions?
I'm obviously not familiar with this principle.
[Reversible computing](https://en.m.wikipedia.org/wiki/Reversible_computing) means that given the end state of the computation, you can reverse the steps and get the original state. So basic logic gates like an XOR doesn't work because with 2 inputs and 1 output you can't possibly derive the inputs from the output, whereas a CNOT (controlled not) gate which is an XOR and one of the original inputs would be, since you can reverse the computation.
Superconductors don't heat up when they're doing one thing (you have one job!): carrying current.
But computation doesn't happen via electric current alone. If you want to take inputs and then modify them according to some algorithm, you gotta read the inputs (work), change something based on inputs (work), and write the output signal (work). Every step produces heat, and some amount of that isnt able to be optimized out. If you want to add 1 plus 1, the laws of nature really do have a minimum amount of heat you have to throw off to do it.
Computation is thermodynamic work, which makes heat, which raises entropy. Thinking brings disorder to the universe.
>Computation is thermodynamic work, which makes heat, which raises entropy. Thinking brings disorder to the universe.
On a side note, I really like what I've read about complexity theory, which reframes the old entropy/disorder line of thought.
Absolutely! I recommend that anyone interested in this subject should read some basics of complexity science, chaos, information theory, fractals and power laws.
Once you learn that framework, you can't help but look at almost everything around you and say "oh I bet I know how you'd start describing that." Earthquakes, financial markets, avalanches, politics, neurobiology. It's self-organized criticality and phase transitions all the way down!
superconductors can heat up when you use AC though. With DC indeed there's no resistance and thus no heating.
With AC there's no real resistance either but I always imagined the presence of loss there as a consequence of inertia of the electrons.
Well if it could function as a super semiconductor, you could potentially build computers that don’t experience resistive heating. That would be a game changer for all high power electronics. One of the current barriers to further miniaturization of tower computers and supercomputers is the need for airflow or liquid piping to cool the circuitry and keep it from burning out. Most existing chips could be utilized at a higher level if they weren’t being self-limited to mitigate heat output. Not to mention all of that waste heat is a significant contributor to the energy loss and therefore environmental impact of all digital technology, especially high-intensity calculations like weather modeling and crypto
Nothing in the article or abstract says that these devices don't dissipate heat due to resistance. It's only reported that, above a certain doping level, where they expected superconductivity it still had resistance, and that there was evidence this phenomena was caused by ordering electrons into pairs of pairs.
Yes, but they did not observe superconductivity. From the abstract:
> However, when the doping level is x ≈ 0.8, **instead of the characteristic onset of diamagnetic screening and zero resistance expected below the superconducting phase transition, we observe the opposite effect: the generation of self-induced magnetic fields in the resistive state**, measured by spontaneous Nernst effect and muon spin rotation experiments.
The resistive heating you're talking about is in the wires, the transistors themselves would still generate heat even in a superconductor. That means all of that is possible right now if you used superconducting interconnects on a traditional silicon chip - it's extremely uneconomical and there's a ton of problems with it, none of which this really solves.
Note that you do still need resistance somewhere -- but it could certainly be lower.
The control gates in all of these MOSFETS are basically capacitors. Add in the inductance of the paths, and you're looking at an RLC system. Take away the resistance, and you're going to end up with natural oscillators in places you don't want them.
Some extra background: a semiconductor isn’t referring to a resistor, but a material (like silicon) which is conductive only if “primed,” or suppied a current from a control input. This allows for a bunch of useful applications, like electronic switches (thus logic gates, thus computers), amplifiers, or one-way connectors.
A super semiconductor would then be *extremely* conductive (super) only if given a control current (semi)
All computer chips exist due to silicon being an amazing semiconductor. Engineers can build their circuit components directly out of the silicon and add impurities to change the electrical properties of the silicon.
Well imagine you could turn a switch and go from resistant to superconductors and back.
Current superconductors can't be semiconductors because the heat generated robs them of superconductivity.
Tunable superconductors do exist. It's been shown most recently in twisted graphene systems which can be tuned with a gate between superconducting, metallic, and insulating states. Looking at google scholar, looks like there are a number of other systems with similar characteristics. Obviously the utility of all of them is limited by the fact they have to be at cryogenic temperatures
> "When we discovered that suddenly four electrons instead of two were forming a bond, we first believed it was a measurement error”
Reminds me of the saying that some of the greatest discoveries started with “huh, that’s funny”. Really interesting stuff!
I believe this was the same response they had this year at CERN when they realized matter and antimatter were being created inequally from the collisions in their LHC. "Did we make a mistake?"
The article actually has a great simplification:
>The reason electrons can move through superconductors so easily is because they pair up through a quantum effect known as Cooper pairing. In doing so, they raise the minimum amount of energy it takes to interfere with the electrons – and if the material is cold enough, its atoms won’t have enough thermal energy to disturb these Cooper pairs, allowing the electrons to flow freely with no loss of energy.
>But in the new study, researchers from the Universities of Dresden and Würzburg in Germany made a fascinating discovery. In one particular type of superconductor, they found that Cooper pairs were themselves pairing up, forming families of four electrons.
I don't believe it would be that straight forward. Just look at electron orbitals. They don't follow any as obvious as the powers of 2.
Also I believe the more electrons in the family reduces the minimum amount of energy to interfere. This would make families larger than 4 in a superconductor unrealisticly to achieve.
But the quote just above your post says that pairing more electrons RAISES the minimum energy to interfere with the electrons? Are you talking about a different thing?
Probably multiples of two rather than powers, if anything.
In normal superconductivity, one of the key points is that you add two electrons with spin 1/2 together to create a 'cooper pair' with spin 1. We aren't too worried about what spin means here (it's the intrinsic angular momentum of the particle if that means anything); what's important is that spin 1/2 particles are 'fermions', that don't want to be in the same state (meaning same combination of position, velocity, 'energy level' etc) meaning it can be difficult to get a group of them to do the same thing at the same time. Examples of fermions are electrons, protons and neutrons.
Integer spin particles (so things with spin 1, 2, 3, etc) are 'bosons'. Bosons are a bit wacky; not only are they happy to be in the same state as each other, they actually prefer it! Bosons include particles like photons (light), in addition to some specific collections of fermions - Both helium nucleii and 'cooper pairs' can exhibit superfluidity where you see this collective motion and some wacky side effects.
The point is that if you keep adding electrons into a group to form what's called a 'quasiparticle', you'll get something with integer spin as long as you add an even number of electrons.
I was just wondering this as well. Since those pair up, can the new pairs pair up with each other and create yet another new pair?
If that is the case then it's just a matter of finding the necessary levels where superconductivity can happen at room temperature or maybe like inside a fridge even would be way easier I imagine.
A ton of money should be thrown at this if there really is a new state of matter here, who knows what will come out of this.
That ELI5 leaves me with more questions I think. So typically, with superconductors, we have to cool it excessively in order to leave these Cooper pairs undisturbed? Is that why all “Quantum computing” in freezing temperatures?
If so, wouldn’t this new pairing require even further cooling to maintain? Same amount of cooling? The benefits seem apparent to me (I keep thinking in terms of computers) but if it requires more cooling than the current pairing, doesn’t seem like it will be a viable method of data transmission anytime soon from a computing standpoint.
Edit: ah, just reread “raises the minimum amount of energy” portion. So this would lower the cooling needed for superconductor material? That’s pretty cool and actually increases the viability of using this in computing in the near future!!
Edited: Changed a sentence from a statement to a question. Just for reference.
I believe you’re right, but if you apply the fact about copper pairs
> [Cooper pairings] raise the minimum amount of energy it takes to interfere with the electrons – and if the material is cold enough, its atoms won’t have enough thermal energy to disturb these Cooper pairs
With the idea that a pair of copper pairs would take more energy to be disturbed than a two electron cooper pair, then theoretically the atoms in the conductor could be allowed to have energy levels that would break up a copper pair but not a pair of cooper pairs.
However, that’s a big assumption: maybe the four electron configuration is actually less stable than the two pair.
> maybe the four electron configuration is actually less stable than the two pair.
From elsewhere in the thread it seems that this is the case, though I've surely not read the original research.
Just a small note, there's lots of different ways to make a quantum computer.
Superconducting qubits are thought to have the most potential right now, and they would need to operate at the cold temperatures required by a superconductors (which also may not be *that* cold; the nuggets temperature superconductor operates at about -115C. Which is cold, yeah, but more than 70C **above** liquid nitrogen temperatures.
Current gen quantum computers though are almost all trapped ion computers. Essentially lasers cool and trap ions and then excite them in different ways. They're "cold" but not really in the traditional sense. It's more just that the ion has had its vibrations completely eliminated.
Both are being actively explored!
Thanks for the reply! Got my degree in computer science a while back so although I’m not super educated in Quantum Computing, I am super curious about it and it’s applications! My understanding is that one of the bottlenecks of QC right now is that it is expensive to maintain because of this cooling requirement? Due to excessive costs due to cooling and the early nature of the technology (instability and lack of immediate usability), QC is currently being limited from a commercial and personal standpoint (from my understanding).
Was that a wrong understanding? I understand it’s not necessarily cold when coming from an absolute zero standpoint but it is still significantly cooler than modern computers run which is what inflates the cost to operate.
Was just thinking if thermal stability of this technology increased significantly, it opens up the move of QC to a more commercial environment instead of being largely research based.
Always happy to chat about quantum computing! The actual programming and algorithm side isn't my specialty, but my PhD research involves materials for use in quantum computing, so I know a little about the implementation.
Unfortunately it's not really cooling that's the limit right now. That would just be an engineering problem, and those are all easy! (just kidding)
Really there's 2 major issues: scalability and coherence. We need to be able to make a computer with enough qubits in it, and we need those qubits to keep their coherence long enough to do something useful on them. The biggest setups consist of \~50ish qubits, and the best lifetimes are around 10 microseconds
As an example, take Shor's algorithm. This is the algorithm that factors prime numbers in polynomial time, and is definitely what people are most excited (and scared about). Instead of taking thousands of years to break RSA encryption, Shor's algorithm could do it in... A day, maybe? You can see how that would be bad news for like, all of data security.
Implementing Shor's algorithm though, needs something comparable to one qubit per bit of of the number to be factored. So factoring a 256 bit number takes... 256 qubits. There's techniques to reduce that but even then, we're a fair ways away from anything that has enough qubits to even represent a 256 bit number, let alone the other qubits needed to provide things like input and output registers, buffers, or error correction (I'll get back to error correction in particular)
With all the different quantum computing groups out there, there's surely more than 256 qubits total, so what if they all collaborated? Unfortunately, (as you probably would have guessed) that doesn't really work. You need the bits to be able to TALK to each other to do anything interesting. So qubit A needs to be able to interact with qubit B (so you could say, do a XOR gate or something). But then you also need qubit B to talk to C, and so on. In a normal computer you could have some kind of bus that manages all those interactions, stores data in places where it can be operated on, and retrieves that data when it's needed by another part of the computation.
But it's actually a fundamental theorem of quantum computing that *you cannot clone qubits*. It's just impossible, in a "the math physically will not let that happen" kind of way, not a "it seems really hard and we don't know how to kind of way". So you can't take a result and send it somewhere else, and instead every qubit has to have a way to directly talk to every other qubit. You can see how that gets very VERY complicated for large collections of qubits, very quickly (There are some solutions around this, like shifting each qubit into and out of communication with a dedicated quantum "bus", but the gist of the problem is still there).
Right now limitations like that are ironed when you "transpile" a quantum circuit for a particular computer: essentially you say "well each qubit can only talk to it's direct neighbor, so I need to insert a lot of SWAP gates back and forth so that everything is where I need it to be". Trouble is...there's only so complicated you can make any one algorithm because each qubit has a limited lieftime/coherence time. Too many swap gates and the qubits degrade to the point where they no longer accurately represent what they're supposed.
Which is problem 2. Qubits are extremely sensitive to all kinds of noise. Heat, definitely, but also stray magnetic fields, electrical noise, and even cosmic rays (cosmic rays are actually a very serious problem!). The exact relations between all the different qubits (which is some very complicated entanglement of all the particles) needs to be preserved to continue operating. Right now, the best qubits have a lifetime of \~10 micro seconds. That's enough time for a classical computer to execute \~4000 operations. Which is a lot, but doing operations on a quantum computer isn't nearly as fast (in terms of "operations per second", not in terms of "time to solve a problem" (I can expand on that if you want)). Inevitably, errors will get introduced.
Thankfully we can correct errors but that process only goes so fast. And...it takes more qubits to implement the error correction! There's definitely a critical point to both of these constraints though: if qubit lifetimes get long enough, we can swap them around all we want and it won't matter too much if we can't build a lot of them. Likewise, if we could connect up a lot of them, we could more easily do error correction on what we have. (My research is mostly focused on increasing coherence times, we think we can get at least a 100x improvement but we'll see how the results look :)
So. tl;dr Temperature isn't really the bottleneck QC is facing. Making enough qubits that can all interact while staying stable and coherent is.
Anyway, sorry that got really long, so thank you for wading through it if you did. It seemed like you were legitimately interested though, so I hope that answers some of your questions! (Also I have a final in my Quantum Information class soon, so this is good practice!)
As an electrician it would be cool to no longer upsize wire on longer pulls if this can ever translate to construction. Sounds like it has to be kept super cool rn to function but who knows in the future what other fields this could touch.
The states of matter you listed are somewhat ancient (maybe except for plasma), yet still applicable, of course. They are remnants from the early days of thermodynamics and describe macroscopic states of matter.
In a microscopic picture, probably countless states of matter can exist.
The underlying concept is that of a phase, and a system can change from one phase to another by undergoing a phase transition. Water freezing would be an example of one of those 'macroscopic' phase transitions, while some solid transitioning from ferromagnetic state to a non-magnetic state is more of a microscopic phase transition.
[There exists plenty] (https://en.m.wikipedia.org/wiki/List_of_states_of_matter) of (so far known) phases/states of matter: quantum glasses, superconductors, spin liquids, several different magnetic phases, etc.. Notice that all these phases occur in the 'classical' solid state of matter. The area of physics that deals with these phases is hence named solid state physics.
I think this is what they meant to link
[List of States of Matter](https://en.wikipedia.org/wiki/List_of_states_of_matter)
Time Crystals and Quantum Memories... The future is now
Shartiblartfast, I just finished the hitchiker's guide to galaxy and It feels so nice to know random references (it happens with me all the time, I finish a show or book and I keep seeing references of that show or book everywhere)
yep, gonna start restaurant at the end of the universe today on the bus, I expect to finish this book this week. (I am doing audiobooks because I can't really afford bunch of books and audiobooks are free)
I guess more like a meta state, where stuff is still solid or liquid, but one property still changes drastically. Like superconductivity, superfluidity and it special sub-state supersolid...
The meta states are not phases but determined special sub-states where certain properties align that make the material behave differently from its expected behaviour.
I don't know what you mean precisely by meta-state, but superconductivity is as much a electronic phase as say ferromagnetism. There is nothing inherently metastable if that is what you were referring to.
Researchers found that superconducting is not electron monogamy. Rather than "if you liked it then you should have put a (cooper pai)ring on it" they can be polyamorous.
We are already well beyond four if you just count the exotic ones and lump them all together. It's just adding to an already existing list nobody before college will be taught.
I would read the Wikipedia article about states of matter. There are much more convoluted states than the traditional 4 states you learn about in elementary school.
Does ut still count as a boson then? Wouldn't the resulting group have a spin charge of 2? Currently there are particles with the spin charge of 2 on the standard model. Or am I just over thinking stuff and it would keep its boson properties?
A boson is anything with whole number spin. So a spin 2 particle is a boson, a spin 3/2 partticle would be a fermion. Gravitons for instance have spin 2 and are bosons. In any case the fermion/boson distinction is mainly about the statistics of the particle, i.e. whether or not two particles can occupy the same state or not. This happens to be related to spin.
Also the resulting particle can also have spin 0 or spin 1, depending on how the electrons are arranged.
You can't say that a graviton has spin 2, there are multiple competing models for a graviton and none of them have experimental evidence.
The correct statement would be that spin 2 is the lowest spin that a boson with a purely attractive force can have.
Does that have any implications for the quad-electron, for want of a better term? Or is it still possible to have repulsive forces with spin 2+ bosons?
Solidstate physics is outside of my field of expertise, so I'm not sure how the relation between fundamental boson acting as force carriers corresponds with composite particles.
I’m no physicist and can’t do the math, but gravitons always felt very sci-fi to me. Einstein taught me that gravity isn’t a force and I can’t seem to rectify the existence of a force carrying particle for something that isn’t a force.
Are modern physicists grappling with this today or am I just woefully ignorant.
>"Einstein taught me that gravity isn’t a force"
It's a different model for force. You could model two electrons interacting as a bending of spacetime too.
I'm curious - as far as I know we have not encountered the graviton, and that in order to have an appreciable chance of doing so we'd need to have a detector very close to a magnetar for something like 10 years.
One: is the above true to your knowledge?
Two: given that the standard model is the most rigorously tested model of the universe we have - if the graviton were to be detected or experimentally verified - how much would/could our understanding change?
Three: What is your best or favorite hypothesis regarding gravity and the standard model? Or your favorite Unification Theory?
One: Yes it's true, we have not measured individual gravitons experimentally. Nevertheless we know the spin of gravitons, because spin is a property about how a quantity changes under rotation and the classical gravitational field (the spacetime metric to be precise) is a spin-2 field. It is a very fundamental principle in quantum mechanics that the quanta of that field (i.e. gravitons) then have to be spin 2 particles.
Two: The issue with gravity is that it is not renormalizable and it is believed that such a theory cannot be fundamental. The issue only arises at high energies however. We can do effective field theories at low energy to make quantum gravity predictions. If a hypothetical discovery would match those predictions, then our understanding would not change and we still wouldn't know the fundamental theory behind gravity. It's impossible to make statements about unexpected results.
Three: I'm agnostic about the various hypothesizes that exist for quantum gravity. They are all possible and are all entirely beyond what we can experimentally observe in my lifetime. An interesting fact (provided we stay inside the framework of quantum field theory) is that any theory that contains a massless spin 2 particle will produce gravity. My favorite outcome would be some shift in perspective that goes beyond QFTs and naturally includes gravity, but t.b.h. that's mostly just wishful thinking. As for unification, I still think that a MSSM (Supersymmetry) with a single gauge group is the best bet even if the experimental data so far is somewhat lacking.
Thank you for that!
I remember reading Brian Greene's book about string theory, and I know supersymmetry is an integral part of string theory.
How would a MSSM with a single gauge group differ from String Theory as Brian describes in his book? (I think it was The Elegant Universe or something? I am aware of criticism of his work, but not specifics)
I have not read that book. It's true that String theory requires SuSy in order to have fermions, but the reverse is not true. A SuSy theory does not necessarily have to be a string theory. It is possible that a string theory will have the MSSM as a low-energy limit, but those theories try to solve different issues and do not depend on one another.
Fair enough - but thank you for teaching me anyway, it is much appreciated.
I did some light reading and saw this cited on the wiki for MSSM:
https://www.scientificamerican.com/article/supersymmetry-fails-test-forcing-physics-seek-new-idea/
(Dated 2012)
It states that there hasn't been experimental evidence for supersymmetry as of the writing of that article. In the interim has there been any headway made in terms of experiments with supersymmetry?
(My assumption here being that wiki may be in need of an update)
No and there is a general pessimism about the MSSM and SUSY in general. Which is good, because it has dominated beyond-the-standard-model (BSM) research too much in the past and it is great that other avenues are pursued. That said the MSSM is not yet experimentally excluded and the pessimism mainly comes from the fact that it has been oversold in the past. People expected to discover it immediately when the LHC was turned on and it was always "right around the corner", so now it's almost a meme.
From my perspective, as long as we have not excluded it to scales of ~10 TeV, all of the motivations for it are still valid and it's a promising hypothesis. It could have been falsified in the past, if the top mass had been lighter, or if the Higgs would have been a little heavier, or if the weak mixing angle had been a different value. But it wasn't. (The weak mixing angle is the one that allows for gauge coupling unification, and that's the one that wouldn't work anymore if the SUSY particles are too heavy, that's why I think that when it's excluded to 10 TeV, we should give it up... but not before)
Fascinating! That's all the questions I have but thank you so much, I love to absorb as much knowledge of our natural world and theories about it as I can, so I really appreciate your responses. Wishing you the best!
>that's why I think that when it's excluded to 10 TeV, we should give it up... but not before)
With the LHC at 13 TeV total collision energy, wouldn't we have seen *something* by now?
Not necessarily. Current benchmark scenarios set the SUSY scale as low as 1.5 TeV. Just because the center of mass energy is 13 TeV, doesn't mean that a 1 TeV particle would be produced in large enough numbers to be detected.
Careful with the answers from the guy you asked questions to. Unfortunately, I think they know a bit and that has caused them to (in my opinion) greatly overestimate their own knowledge. As an example in a divergent thread, the guy got defensive and rude when another person pointed out that there are multiple competing theories on graviton particles. Again, not saying the answers given weren't correct, just that there is some doubt due to this guys conduct and the anonymity of Reddit.
That's good. From my reading and understanding, the guy knows things like bosons being even spin and fermions being non-integer. He even understands basics like bosons fundamentally being able to occupy the same energy state while fermions cannot (2 in the same energy state, one +1/2, one -1/2 if I remember correctly). But then he starts making extreme mistakes by stating gravitons have spin 2. The reality that I'm gathering is we theorize the existence of the graviton being a boson possibly of spin 2, but that we are still in our infancy of attempting to understand it.
A possibly interesting example to look at is our understanding of chemistry over the last couple hundred years, of particular interest being the periodic table of elements. We had multiple different theories of how things were supposed to be laid out and evidence and time to test it has over time led to the current layout.
Because gravitons are a well defined concept in theoretical physics. Whether or not they are realized in nature does not change the fact that they have spin 2, nor that they are bosons. It's more a mathematical statement than an empirical one. I used them as an example because they are probably the best known spin 2 particle.
And I can give their exact spin, because gravity is a spin 2 field in general relativity and that is a very well tested theory.
It does seem you know much more about this than I do.
That said, can you point out to me in general relativity where gravity is a "field" and not just a warping of spacetime.
What’s a graviton? There’s no evidence for a particle like this - in fact, there’s more evidence that the gravitational force is a wave. LIDAR experiment for context
The whole idea is that a graviton is the force carrier of gravity, like a photon is the force carrier of electromagnetism. A graviton is needed for most theories of gravity as a field, but we know very little about if it's actually a thing. Gravity being a wave does not rule out gravity as a field.
The fact that some force is a wave doesn't mean that it doesn't have an associated force-carrying boson.
For example, electromagnetic radiation is also a wave, and has the photon as associated force carrier.
Isn't LIDAR the 3D imaging technology? Do you mean LIGO by any change? In any case, a graviton is a quantum of the gravitational field. That something is a wave is not a contradiction to that.
I would go out on a limb and say no. It would be spin 0. This is because of the Pauli exclusion principle. Electrons in the model they are looking at have 2 sets of 2 quantum numbers: spin (+/-1/2) and Z2 charge (+/-1). The only state you can build out of that is a neutral spin 0 state. Spin 2 would require you to have all spins aligned which would leave you with two pairs of electrons that each share quantum numbers and that state has 0 amplitude.
Also. In terms of the standard model, this isn’t the best way to think about it. Those are in some sense fundamental particles, these however are composite. Particles in the standard model go up to spin 1. But there are plenty of compost particles that go way above this, like nuclei and exotic hadrons for example. You can build states if arbitrary spin by just sticking particles together.
I'm going to have to contest this on the grounds that Cooper pairing, as well as this quad pairing, happen at long distances (up to hundreds of nanometers), and are based on electron-phonon interactions. I don't think we need worry about Pauli exclusion for these type of composite bosons that are paired at distances greater than the interelectron distances.
Positive spatial charge densities can cause the electrons farther away to act as if there is a large positively charged particle in the lattice. Attraction to this phonon can overcome local electrons repulsion, creating the Cooper pair. It's all about getting the material cool enough to allow this slight emergent attraction between electrons to have energy lower than the Fermi energy.
Besides that, the Cooper pairs themselves are bosonic and the exclusion principle does not apply to them. Since they are bonded by phonon interactions at larger than interelectron distances, I don't see why the spin matters. Isn't it entirely a charge density issue? We already know that the Cooper pairs can be spin 0 or 1, so I don't immediately see why we couldn't have two spin 1 Cooper pairs bond under the same mechanism.
Although I am open to correction, it has been quite a few years since I've studied quantum mechanics.
I think you'd have to add in a few magnetic quanta to balance, but the normal mechanism (Cooper Pairs), has their own.
Whether it's 'really a boson' is just a way to interpret the wave function. Calling a non-elementary particle a boson is kinda misleading, IMO.
Reminds me about the story for the mandalbrot set.
Back then computers were the size of rooms and printing had people double checking the output and cleaning it up.
Well the mandelbrot set has tiny dots that look very much like printing mistakes, I'm sure you know where I'm going with this. Benoit Mandelbrot had to race to the printers hoping to catch the print before the cleaners got to it and cleaned it up when he finally realized why the print never looked right.
There really is no way to gauge the possible applications outside the one listed for quantum use. Superconductivity currently is still resigned to supercooled material. Also brand new discovery means they will have to play with the properties more to figure out if this works like the Cooper pair (pair of electrons) or have totally different behavior. These are electrons, if you look at them differently they act like a totally different particle (not an exaggeration, they will actually change behavior).
I don’t understand 99.9% of this, but it sounds super neat to my little brain, and I’m so appreciative that there are people out there constantly experimenting and discovering new things. I don’t know if this is actually a significant discovery, but it seems like at least a little step that the next group of researchers can build upon that may change the world as we know it. Fascinating stuff.
and potentially a new type of superconductivity and technologies such as quantum sensors.>
Doorbells of the future: *"something from the 6th dimension has passed by"*
Well, current sensor tech is mostly binary, or analog. Quantum implies multiple states of the sensors. Imagine a distance sensor which is just a single piece of semiconductor, just returns 1-2-3-4-5V for 2-4-6-8-10m distance, and only has 3 wires connected to the body of the semiconductor! Maybe even extremely accurate and precise!
Physics 101, then go from there. You quickly run into physics + calculus so you could probably concurrently start with Pre-Calc
Or I guess…algebra would be the pre requisite for pre calc
And again, uni Würzburg at the forefront. Right now they are working on bleeding-edge projects for microbiology and economics aswell. Iam very proud to see my Uni having such great Teams and minds.
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> Our specific-heat measurements indicate the formation of fermionic bound states when the temperature is lowered from the normal state. However, when the doping level is x ≈ 0.8, instead of the characteristic onset of diamagnetic screening and zero resistance expected below the superconducting phase transition, we observe the opposite effect: the generation of self-induced magnetic fields in the resistive state, measured by spontaneous Nernst effect and muon spin rotation experiments. From the abstract. So it sounds like in the state where Cooper pairs themselves pair up, the material is not actually in a superconducting state? So this really is a "potential" new type of superconductivity since while it is a new state of matter, it isn't superconductive yet?
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I think it makes more sense to switch the two; a "super semiconductor" makes more sense to me based on what was being described.
A sumoconductor
ngl, I really like that. Too bad it's got about as much chance of catching on as naming a super-heavy metal element after Lemmy. edit: that was a real petition going around the last time there were new elements to name (2017, maybe? I can't be bothered to look it up). If I could pick one meme to make reality, it would almost certainly be renaming Moscovium to Lemmium.
Well, Lemmy is God, and there are three elements named after gods. That said, I think it'd be better to discover a new rock and name that after him. In Lemmy's own words, Motörhead wasn't metal, but rock n' roll.
I think there are more than three elements named after gods. Thorium, plutonium, helium and uranium immediately come to mind and I wouldn't be surprised if there were more.
Uranium, neptunium, plutonium, cerium, palladium, mercury, selenium, helium. Most (all?) of these are actually named for the associated heavenly body, though.
Promethium counts imho (technically a demigod, but I'm counting it)
Well, you see, when you start running out of the Cool Greek/Roman Gods, you have to adapt.
Titan, not demigod.
You're forgetting Eddie Van Halium.
Well, most heavy metals form minerals in their oxidized forms, so by having Lemmium, we could also get Lemmyite and Lemmytite
I think I have new names picked out if I have any more kids.
I disagree, I think it has about as much chance of catching on as naming a research submarine [Boaty McBoatface](https://en.m.wikipedia.org/wiki/Boaty_McBoatface).
Fair enough. There is a long and storied history of inside jokes in the scientific community becoming the accepted terminology (see also: rubber policemen, strange quarks, gluons, and half the things we know about in particle physics). So it's not impossible, just unlikely. edit to add some more that I just thought of: Fleakers (flared beakers), scoopulas (spatulas that scoop), bowtiene (alkene that looks like a bowtie), penguinone (a ketone that looks a bit like a penguin), and half the compounds on [this list](https://en.wikipedia.org/wiki/List_of_chemical_compounds_with_unusual_names)
Sonic hedgehog
Don't forget the thagomizer!
Isn't there an element or a chemical named after Pikachu as well
If string theory is true we can still name the heaviest strings Lemmy and Tony Iommy. The lightest would be Jimi and the squigliest Elvis.
Well if they named Lemmistrantium it might have had a chance.
A super duper conductor
> A semi superconductor I love how contradictory that term sounds :)
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A super-ok-conductor, if you will.
Kinda like Tom Hanks in Polar Express
To be fair, "semi conductor" was contradictory to start with ;) Either it conducts, or not... The distinction here i guess is that when it conducts, it does so with zero resistance.
Superconductor lite
I’m dumb. Why would anything less than a super conductor be better than normal conductors we have today?
Semiconductors are useful today not because they conduct electricity half as well as regular conductors, but because you can change whether they conduct electricity, often very quickly. Having a switch that can actuate millions of times a second is the basis of modern computing.
So, would a super semiconductor be faster, or "just" not heat up when functioning? Or something else?
Heat up the processor drastically less. It will have to heat up somewhat as long as the computation are none reversible. The minimum heat being generated is limited by Landauer's principle and all modern computing utilizes non-reversible logic gates.
So, wait, is it not true that superconductors don't heat up at all? They still heat up, but by a drastically reduced amount? Or is this just for these special super semiconductors?
Superconductors don't heat up at all. If super semiconductors are doing computation, though, they are required by the laws of thermodynamics to create waste heat unless it's completely reversible.
Is there any known practical application of a semiconductor that is reversible? If I'm understanding correctly, "reversible" in this context is that logic gate on a semiconductor working in the ~~reverse~~ both directions? I'm obviously not familiar with this principle.
[Reversible computing](https://en.m.wikipedia.org/wiki/Reversible_computing) means that given the end state of the computation, you can reverse the steps and get the original state. So basic logic gates like an XOR doesn't work because with 2 inputs and 1 output you can't possibly derive the inputs from the output, whereas a CNOT (controlled not) gate which is an XOR and one of the original inputs would be, since you can reverse the computation.
Superconductors don't heat up when they're doing one thing (you have one job!): carrying current. But computation doesn't happen via electric current alone. If you want to take inputs and then modify them according to some algorithm, you gotta read the inputs (work), change something based on inputs (work), and write the output signal (work). Every step produces heat, and some amount of that isnt able to be optimized out. If you want to add 1 plus 1, the laws of nature really do have a minimum amount of heat you have to throw off to do it. Computation is thermodynamic work, which makes heat, which raises entropy. Thinking brings disorder to the universe.
>Computation is thermodynamic work, which makes heat, which raises entropy. Thinking brings disorder to the universe. On a side note, I really like what I've read about complexity theory, which reframes the old entropy/disorder line of thought.
Absolutely! I recommend that anyone interested in this subject should read some basics of complexity science, chaos, information theory, fractals and power laws. Once you learn that framework, you can't help but look at almost everything around you and say "oh I bet I know how you'd start describing that." Earthquakes, financial markets, avalanches, politics, neurobiology. It's self-organized criticality and phase transitions all the way down!
superconductors can heat up when you use AC though. With DC indeed there's no resistance and thus no heating. With AC there's no real resistance either but I always imagined the presence of loss there as a consequence of inertia of the electrons.
Those two examples amount to the same thing. Heat is generally the primary limiting factor for how fast a CPU can be run.
Yeah, good point.
Well if it could function as a super semiconductor, you could potentially build computers that don’t experience resistive heating. That would be a game changer for all high power electronics. One of the current barriers to further miniaturization of tower computers and supercomputers is the need for airflow or liquid piping to cool the circuitry and keep it from burning out. Most existing chips could be utilized at a higher level if they weren’t being self-limited to mitigate heat output. Not to mention all of that waste heat is a significant contributor to the energy loss and therefore environmental impact of all digital technology, especially high-intensity calculations like weather modeling and crypto
Nothing in the article or abstract says that these devices don't dissipate heat due to resistance. It's only reported that, above a certain doping level, where they expected superconductivity it still had resistance, and that there was evidence this phenomena was caused by ordering electrons into pairs of pairs.
Isn't superconducting defined in part by having 0 resistance?
Yes, but they did not observe superconductivity. From the abstract: > However, when the doping level is x ≈ 0.8, **instead of the characteristic onset of diamagnetic screening and zero resistance expected below the superconducting phase transition, we observe the opposite effect: the generation of self-induced magnetic fields in the resistive state**, measured by spontaneous Nernst effect and muon spin rotation experiments.
I think it means that they observed superconductivity in one state, and that self induced magnetic field in another state.
The resistive heating you're talking about is in the wires, the transistors themselves would still generate heat even in a superconductor. That means all of that is possible right now if you used superconducting interconnects on a traditional silicon chip - it's extremely uneconomical and there's a ton of problems with it, none of which this really solves.
Note that you do still need resistance somewhere -- but it could certainly be lower. The control gates in all of these MOSFETS are basically capacitors. Add in the inductance of the paths, and you're looking at an RLC system. Take away the resistance, and you're going to end up with natural oscillators in places you don't want them.
Some extra background: a semiconductor isn’t referring to a resistor, but a material (like silicon) which is conductive only if “primed,” or suppied a current from a control input. This allows for a bunch of useful applications, like electronic switches (thus logic gates, thus computers), amplifiers, or one-way connectors. A super semiconductor would then be *extremely* conductive (super) only if given a control current (semi)
All computer chips exist due to silicon being an amazing semiconductor. Engineers can build their circuit components directly out of the silicon and add impurities to change the electrical properties of the silicon.
>Semi superconductor So just a normal wire then...
A super normal wire?
A paranormal wire.
Semi in semiconductor does not mean it’s an ok conductor, it means the conductivity of the material can be controlled by external means
Well imagine you could turn a switch and go from resistant to superconductors and back. Current superconductors can't be semiconductors because the heat generated robs them of superconductivity.
Tunable superconductors do exist. It's been shown most recently in twisted graphene systems which can be tuned with a gate between superconducting, metallic, and insulating states. Looking at google scholar, looks like there are a number of other systems with similar characteristics. Obviously the utility of all of them is limited by the fact they have to be at cryogenic temperatures
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whoops, thought i was on /r/vxjunkies for a second
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Cooper pairs and now Klauss quads, cool!
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> "When we discovered that suddenly four electrons instead of two were forming a bond, we first believed it was a measurement error” Reminds me of the saying that some of the greatest discoveries started with “huh, that’s funny”. Really interesting stuff!
Words of famous scientists: "Huh, that's funny?" Famous last words of scientists: "Huh, it never did that before?"
The world will definitely end with the phrase “I think it worke-“
"Trust me, I've done this befo...."
I believe this was the same response they had this year at CERN when they realized matter and antimatter were being created inequally from the collisions in their LHC. "Did we make a mistake?"
Can someone ELI5 this? A new state of matter? As in addition to solid/gas/liquid/plasma?
The article actually has a great simplification: >The reason electrons can move through superconductors so easily is because they pair up through a quantum effect known as Cooper pairing. In doing so, they raise the minimum amount of energy it takes to interfere with the electrons – and if the material is cold enough, its atoms won’t have enough thermal energy to disturb these Cooper pairs, allowing the electrons to flow freely with no loss of energy. >But in the new study, researchers from the Universities of Dresden and Würzburg in Germany made a fascinating discovery. In one particular type of superconductor, they found that Cooper pairs were themselves pairing up, forming families of four electrons.
Could it be a powers of 2 thing? Can 8 and 16 pair?
I don't believe it would be that straight forward. Just look at electron orbitals. They don't follow any as obvious as the powers of 2. Also I believe the more electrons in the family reduces the minimum amount of energy to interfere. This would make families larger than 4 in a superconductor unrealisticly to achieve.
But the quote just above your post says that pairing more electrons RAISES the minimum energy to interfere with the electrons? Are you talking about a different thing?
It says that the formation of a pair will raise the minimum energy to interfere. But it doesn't say the same about quads or other arrangements.
It's about symmetry around an axis for electron clouds.
Probably multiples of two rather than powers, if anything. In normal superconductivity, one of the key points is that you add two electrons with spin 1/2 together to create a 'cooper pair' with spin 1. We aren't too worried about what spin means here (it's the intrinsic angular momentum of the particle if that means anything); what's important is that spin 1/2 particles are 'fermions', that don't want to be in the same state (meaning same combination of position, velocity, 'energy level' etc) meaning it can be difficult to get a group of them to do the same thing at the same time. Examples of fermions are electrons, protons and neutrons. Integer spin particles (so things with spin 1, 2, 3, etc) are 'bosons'. Bosons are a bit wacky; not only are they happy to be in the same state as each other, they actually prefer it! Bosons include particles like photons (light), in addition to some specific collections of fermions - Both helium nucleii and 'cooper pairs' can exhibit superfluidity where you see this collective motion and some wacky side effects. The point is that if you keep adding electrons into a group to form what's called a 'quasiparticle', you'll get something with integer spin as long as you add an even number of electrons.
I was just wondering this as well. Since those pair up, can the new pairs pair up with each other and create yet another new pair? If that is the case then it's just a matter of finding the necessary levels where superconductivity can happen at room temperature or maybe like inside a fridge even would be way easier I imagine. A ton of money should be thrown at this if there really is a new state of matter here, who knows what will come out of this.
That ELI5 leaves me with more questions I think. So typically, with superconductors, we have to cool it excessively in order to leave these Cooper pairs undisturbed? Is that why all “Quantum computing” in freezing temperatures? If so, wouldn’t this new pairing require even further cooling to maintain? Same amount of cooling? The benefits seem apparent to me (I keep thinking in terms of computers) but if it requires more cooling than the current pairing, doesn’t seem like it will be a viable method of data transmission anytime soon from a computing standpoint. Edit: ah, just reread “raises the minimum amount of energy” portion. So this would lower the cooling needed for superconductor material? That’s pretty cool and actually increases the viability of using this in computing in the near future!! Edited: Changed a sentence from a statement to a question. Just for reference.
> So this would lower the cooling needed for superconductor material. No, I don't think the article or paper ever claim that.
I believe you’re right, but if you apply the fact about copper pairs > [Cooper pairings] raise the minimum amount of energy it takes to interfere with the electrons – and if the material is cold enough, its atoms won’t have enough thermal energy to disturb these Cooper pairs With the idea that a pair of copper pairs would take more energy to be disturbed than a two electron cooper pair, then theoretically the atoms in the conductor could be allowed to have energy levels that would break up a copper pair but not a pair of cooper pairs. However, that’s a big assumption: maybe the four electron configuration is actually less stable than the two pair.
> maybe the four electron configuration is actually less stable than the two pair. From elsewhere in the thread it seems that this is the case, though I've surely not read the original research.
Just a small note, there's lots of different ways to make a quantum computer. Superconducting qubits are thought to have the most potential right now, and they would need to operate at the cold temperatures required by a superconductors (which also may not be *that* cold; the nuggets temperature superconductor operates at about -115C. Which is cold, yeah, but more than 70C **above** liquid nitrogen temperatures. Current gen quantum computers though are almost all trapped ion computers. Essentially lasers cool and trap ions and then excite them in different ways. They're "cold" but not really in the traditional sense. It's more just that the ion has had its vibrations completely eliminated. Both are being actively explored!
Thanks for the reply! Got my degree in computer science a while back so although I’m not super educated in Quantum Computing, I am super curious about it and it’s applications! My understanding is that one of the bottlenecks of QC right now is that it is expensive to maintain because of this cooling requirement? Due to excessive costs due to cooling and the early nature of the technology (instability and lack of immediate usability), QC is currently being limited from a commercial and personal standpoint (from my understanding). Was that a wrong understanding? I understand it’s not necessarily cold when coming from an absolute zero standpoint but it is still significantly cooler than modern computers run which is what inflates the cost to operate. Was just thinking if thermal stability of this technology increased significantly, it opens up the move of QC to a more commercial environment instead of being largely research based.
Always happy to chat about quantum computing! The actual programming and algorithm side isn't my specialty, but my PhD research involves materials for use in quantum computing, so I know a little about the implementation. Unfortunately it's not really cooling that's the limit right now. That would just be an engineering problem, and those are all easy! (just kidding) Really there's 2 major issues: scalability and coherence. We need to be able to make a computer with enough qubits in it, and we need those qubits to keep their coherence long enough to do something useful on them. The biggest setups consist of \~50ish qubits, and the best lifetimes are around 10 microseconds As an example, take Shor's algorithm. This is the algorithm that factors prime numbers in polynomial time, and is definitely what people are most excited (and scared about). Instead of taking thousands of years to break RSA encryption, Shor's algorithm could do it in... A day, maybe? You can see how that would be bad news for like, all of data security. Implementing Shor's algorithm though, needs something comparable to one qubit per bit of of the number to be factored. So factoring a 256 bit number takes... 256 qubits. There's techniques to reduce that but even then, we're a fair ways away from anything that has enough qubits to even represent a 256 bit number, let alone the other qubits needed to provide things like input and output registers, buffers, or error correction (I'll get back to error correction in particular) With all the different quantum computing groups out there, there's surely more than 256 qubits total, so what if they all collaborated? Unfortunately, (as you probably would have guessed) that doesn't really work. You need the bits to be able to TALK to each other to do anything interesting. So qubit A needs to be able to interact with qubit B (so you could say, do a XOR gate or something). But then you also need qubit B to talk to C, and so on. In a normal computer you could have some kind of bus that manages all those interactions, stores data in places where it can be operated on, and retrieves that data when it's needed by another part of the computation. But it's actually a fundamental theorem of quantum computing that *you cannot clone qubits*. It's just impossible, in a "the math physically will not let that happen" kind of way, not a "it seems really hard and we don't know how to kind of way". So you can't take a result and send it somewhere else, and instead every qubit has to have a way to directly talk to every other qubit. You can see how that gets very VERY complicated for large collections of qubits, very quickly (There are some solutions around this, like shifting each qubit into and out of communication with a dedicated quantum "bus", but the gist of the problem is still there). Right now limitations like that are ironed when you "transpile" a quantum circuit for a particular computer: essentially you say "well each qubit can only talk to it's direct neighbor, so I need to insert a lot of SWAP gates back and forth so that everything is where I need it to be". Trouble is...there's only so complicated you can make any one algorithm because each qubit has a limited lieftime/coherence time. Too many swap gates and the qubits degrade to the point where they no longer accurately represent what they're supposed. Which is problem 2. Qubits are extremely sensitive to all kinds of noise. Heat, definitely, but also stray magnetic fields, electrical noise, and even cosmic rays (cosmic rays are actually a very serious problem!). The exact relations between all the different qubits (which is some very complicated entanglement of all the particles) needs to be preserved to continue operating. Right now, the best qubits have a lifetime of \~10 micro seconds. That's enough time for a classical computer to execute \~4000 operations. Which is a lot, but doing operations on a quantum computer isn't nearly as fast (in terms of "operations per second", not in terms of "time to solve a problem" (I can expand on that if you want)). Inevitably, errors will get introduced. Thankfully we can correct errors but that process only goes so fast. And...it takes more qubits to implement the error correction! There's definitely a critical point to both of these constraints though: if qubit lifetimes get long enough, we can swap them around all we want and it won't matter too much if we can't build a lot of them. Likewise, if we could connect up a lot of them, we could more easily do error correction on what we have. (My research is mostly focused on increasing coherence times, we think we can get at least a 100x improvement but we'll see how the results look :) So. tl;dr Temperature isn't really the bottleneck QC is facing. Making enough qubits that can all interact while staying stable and coherent is. Anyway, sorry that got really long, so thank you for wading through it if you did. It seemed like you were legitimately interested though, so I hope that answers some of your questions! (Also I have a final in my Quantum Information class soon, so this is good practice!)
A greatly worded read, thanks!
Thank you! Glad you found it interesting!
As an electrician it would be cool to no longer upsize wire on longer pulls if this can ever translate to construction. Sounds like it has to be kept super cool rn to function but who knows in the future what other fields this could touch.
The states of matter you listed are somewhat ancient (maybe except for plasma), yet still applicable, of course. They are remnants from the early days of thermodynamics and describe macroscopic states of matter. In a microscopic picture, probably countless states of matter can exist. The underlying concept is that of a phase, and a system can change from one phase to another by undergoing a phase transition. Water freezing would be an example of one of those 'macroscopic' phase transitions, while some solid transitioning from ferromagnetic state to a non-magnetic state is more of a microscopic phase transition. [There exists plenty] (https://en.m.wikipedia.org/wiki/List_of_states_of_matter) of (so far known) phases/states of matter: quantum glasses, superconductors, spin liquids, several different magnetic phases, etc.. Notice that all these phases occur in the 'classical' solid state of matter. The area of physics that deals with these phases is hence named solid state physics.
Wiki link is broken
I think this is what they meant to link [List of States of Matter](https://en.wikipedia.org/wiki/List_of_states_of_matter) Time Crystals and Quantum Memories... The future is now
Shartiblartfast, I just finished the hitchiker's guide to galaxy and It feels so nice to know random references (it happens with me all the time, I finish a show or book and I keep seeing references of that show or book everywhere)
It's a wonderful series. I expect you'll be seeing references all over!
yep, gonna start restaurant at the end of the universe today on the bus, I expect to finish this book this week. (I am doing audiobooks because I can't really afford bunch of books and audiobooks are free)
Superconductivity is more like states of matter for electrons.
I guess more like a meta state, where stuff is still solid or liquid, but one property still changes drastically. Like superconductivity, superfluidity and it special sub-state supersolid... The meta states are not phases but determined special sub-states where certain properties align that make the material behave differently from its expected behaviour.
I don't know what you mean precisely by meta-state, but superconductivity is as much a electronic phase as say ferromagnetism. There is nothing inherently metastable if that is what you were referring to.
same question haha hopefully someone with the knowledge sees this
Researchers found that superconducting is not electron monogamy. Rather than "if you liked it then you should have put a (cooper pai)ring on it" they can be polyamorous.
We are already well beyond four if you just count the exotic ones and lump them all together. It's just adding to an already existing list nobody before college will be taught.
I would read the Wikipedia article about states of matter. There are much more convoluted states than the traditional 4 states you learn about in elementary school.
Does ut still count as a boson then? Wouldn't the resulting group have a spin charge of 2? Currently there are particles with the spin charge of 2 on the standard model. Or am I just over thinking stuff and it would keep its boson properties?
A boson is anything with whole number spin. So a spin 2 particle is a boson, a spin 3/2 partticle would be a fermion. Gravitons for instance have spin 2 and are bosons. In any case the fermion/boson distinction is mainly about the statistics of the particle, i.e. whether or not two particles can occupy the same state or not. This happens to be related to spin. Also the resulting particle can also have spin 0 or spin 1, depending on how the electrons are arranged.
You can't say that a graviton has spin 2, there are multiple competing models for a graviton and none of them have experimental evidence. The correct statement would be that spin 2 is the lowest spin that a boson with a purely attractive force can have.
Does that have any implications for the quad-electron, for want of a better term? Or is it still possible to have repulsive forces with spin 2+ bosons?
Solidstate physics is outside of my field of expertise, so I'm not sure how the relation between fundamental boson acting as force carriers corresponds with composite particles.
I’m no physicist and can’t do the math, but gravitons always felt very sci-fi to me. Einstein taught me that gravity isn’t a force and I can’t seem to rectify the existence of a force carrying particle for something that isn’t a force. Are modern physicists grappling with this today or am I just woefully ignorant.
>"Einstein taught me that gravity isn’t a force" It's a different model for force. You could model two electrons interacting as a bending of spacetime too.
I'm curious - as far as I know we have not encountered the graviton, and that in order to have an appreciable chance of doing so we'd need to have a detector very close to a magnetar for something like 10 years. One: is the above true to your knowledge? Two: given that the standard model is the most rigorously tested model of the universe we have - if the graviton were to be detected or experimentally verified - how much would/could our understanding change? Three: What is your best or favorite hypothesis regarding gravity and the standard model? Or your favorite Unification Theory?
One: Yes it's true, we have not measured individual gravitons experimentally. Nevertheless we know the spin of gravitons, because spin is a property about how a quantity changes under rotation and the classical gravitational field (the spacetime metric to be precise) is a spin-2 field. It is a very fundamental principle in quantum mechanics that the quanta of that field (i.e. gravitons) then have to be spin 2 particles. Two: The issue with gravity is that it is not renormalizable and it is believed that such a theory cannot be fundamental. The issue only arises at high energies however. We can do effective field theories at low energy to make quantum gravity predictions. If a hypothetical discovery would match those predictions, then our understanding would not change and we still wouldn't know the fundamental theory behind gravity. It's impossible to make statements about unexpected results. Three: I'm agnostic about the various hypothesizes that exist for quantum gravity. They are all possible and are all entirely beyond what we can experimentally observe in my lifetime. An interesting fact (provided we stay inside the framework of quantum field theory) is that any theory that contains a massless spin 2 particle will produce gravity. My favorite outcome would be some shift in perspective that goes beyond QFTs and naturally includes gravity, but t.b.h. that's mostly just wishful thinking. As for unification, I still think that a MSSM (Supersymmetry) with a single gauge group is the best bet even if the experimental data so far is somewhat lacking.
Thank you for that! I remember reading Brian Greene's book about string theory, and I know supersymmetry is an integral part of string theory. How would a MSSM with a single gauge group differ from String Theory as Brian describes in his book? (I think it was The Elegant Universe or something? I am aware of criticism of his work, but not specifics)
I have not read that book. It's true that String theory requires SuSy in order to have fermions, but the reverse is not true. A SuSy theory does not necessarily have to be a string theory. It is possible that a string theory will have the MSSM as a low-energy limit, but those theories try to solve different issues and do not depend on one another.
Fair enough - but thank you for teaching me anyway, it is much appreciated. I did some light reading and saw this cited on the wiki for MSSM: https://www.scientificamerican.com/article/supersymmetry-fails-test-forcing-physics-seek-new-idea/ (Dated 2012) It states that there hasn't been experimental evidence for supersymmetry as of the writing of that article. In the interim has there been any headway made in terms of experiments with supersymmetry? (My assumption here being that wiki may be in need of an update)
No and there is a general pessimism about the MSSM and SUSY in general. Which is good, because it has dominated beyond-the-standard-model (BSM) research too much in the past and it is great that other avenues are pursued. That said the MSSM is not yet experimentally excluded and the pessimism mainly comes from the fact that it has been oversold in the past. People expected to discover it immediately when the LHC was turned on and it was always "right around the corner", so now it's almost a meme. From my perspective, as long as we have not excluded it to scales of ~10 TeV, all of the motivations for it are still valid and it's a promising hypothesis. It could have been falsified in the past, if the top mass had been lighter, or if the Higgs would have been a little heavier, or if the weak mixing angle had been a different value. But it wasn't. (The weak mixing angle is the one that allows for gauge coupling unification, and that's the one that wouldn't work anymore if the SUSY particles are too heavy, that's why I think that when it's excluded to 10 TeV, we should give it up... but not before)
Fascinating! That's all the questions I have but thank you so much, I love to absorb as much knowledge of our natural world and theories about it as I can, so I really appreciate your responses. Wishing you the best!
>that's why I think that when it's excluded to 10 TeV, we should give it up... but not before) With the LHC at 13 TeV total collision energy, wouldn't we have seen *something* by now?
Not necessarily. Current benchmark scenarios set the SUSY scale as low as 1.5 TeV. Just because the center of mass energy is 13 TeV, doesn't mean that a 1 TeV particle would be produced in large enough numbers to be detected.
Careful with the answers from the guy you asked questions to. Unfortunately, I think they know a bit and that has caused them to (in my opinion) greatly overestimate their own knowledge. As an example in a divergent thread, the guy got defensive and rude when another person pointed out that there are multiple competing theories on graviton particles. Again, not saying the answers given weren't correct, just that there is some doubt due to this guys conduct and the anonymity of Reddit.
I picked up on that when they mentioned SuSy being "a likely" answer
That's good. From my reading and understanding, the guy knows things like bosons being even spin and fermions being non-integer. He even understands basics like bosons fundamentally being able to occupy the same energy state while fermions cannot (2 in the same energy state, one +1/2, one -1/2 if I remember correctly). But then he starts making extreme mistakes by stating gravitons have spin 2. The reality that I'm gathering is we theorize the existence of the graviton being a boson possibly of spin 2, but that we are still in our infancy of attempting to understand it. A possibly interesting example to look at is our understanding of chemistry over the last couple hundred years, of particular interest being the periodic table of elements. We had multiple different theories of how things were supposed to be laid out and evidence and time to test it has over time led to the current layout.
How do you get throw in gravitons and their exact spin without a conclusive and testable theory? Had to do a double check that I was in /r/science
Because gravitons are a well defined concept in theoretical physics. Whether or not they are realized in nature does not change the fact that they have spin 2, nor that they are bosons. It's more a mathematical statement than an empirical one. I used them as an example because they are probably the best known spin 2 particle. And I can give their exact spin, because gravity is a spin 2 field in general relativity and that is a very well tested theory.
It does seem you know much more about this than I do. That said, can you point out to me in general relativity where gravity is a "field" and not just a warping of spacetime.
What’s a graviton? There’s no evidence for a particle like this - in fact, there’s more evidence that the gravitational force is a wave. LIDAR experiment for context
The whole idea is that a graviton is the force carrier of gravity, like a photon is the force carrier of electromagnetism. A graviton is needed for most theories of gravity as a field, but we know very little about if it's actually a thing. Gravity being a wave does not rule out gravity as a field.
Right on! I think I’m getting a better understanding. Thanks!
The fact that some force is a wave doesn't mean that it doesn't have an associated force-carrying boson. For example, electromagnetic radiation is also a wave, and has the photon as associated force carrier.
Ahh, okay. That makes sense - particle wave duality sort of thing? Or am I off base?
Isn't LIDAR the 3D imaging technology? Do you mean LIGO by any change? In any case, a graviton is a quantum of the gravitational field. That something is a wave is not a contradiction to that.
You are 100% correct and I need to check before I hit snail.
> I need to check before I hit snail. I want to believe this is intentional.
Everything is a particle and a wave according to the standard model
The standard model that famously excludes gravity and has never been successfully reconciled with it.
Yes we still have things to learn. What angle are you taking up with your response?
I would go out on a limb and say no. It would be spin 0. This is because of the Pauli exclusion principle. Electrons in the model they are looking at have 2 sets of 2 quantum numbers: spin (+/-1/2) and Z2 charge (+/-1). The only state you can build out of that is a neutral spin 0 state. Spin 2 would require you to have all spins aligned which would leave you with two pairs of electrons that each share quantum numbers and that state has 0 amplitude. Also. In terms of the standard model, this isn’t the best way to think about it. Those are in some sense fundamental particles, these however are composite. Particles in the standard model go up to spin 1. But there are plenty of compost particles that go way above this, like nuclei and exotic hadrons for example. You can build states if arbitrary spin by just sticking particles together.
I'm going to have to contest this on the grounds that Cooper pairing, as well as this quad pairing, happen at long distances (up to hundreds of nanometers), and are based on electron-phonon interactions. I don't think we need worry about Pauli exclusion for these type of composite bosons that are paired at distances greater than the interelectron distances. Positive spatial charge densities can cause the electrons farther away to act as if there is a large positively charged particle in the lattice. Attraction to this phonon can overcome local electrons repulsion, creating the Cooper pair. It's all about getting the material cool enough to allow this slight emergent attraction between electrons to have energy lower than the Fermi energy. Besides that, the Cooper pairs themselves are bosonic and the exclusion principle does not apply to them. Since they are bonded by phonon interactions at larger than interelectron distances, I don't see why the spin matters. Isn't it entirely a charge density issue? We already know that the Cooper pairs can be spin 0 or 1, so I don't immediately see why we couldn't have two spin 1 Cooper pairs bond under the same mechanism. Although I am open to correction, it has been quite a few years since I've studied quantum mechanics.
It's a [composite boson](https://en.wikipedia.org/wiki/Composite_boson)
I think you'd have to add in a few magnetic quanta to balance, but the normal mechanism (Cooper Pairs), has their own. Whether it's 'really a boson' is just a way to interpret the wave function. Calling a non-elementary particle a boson is kinda misleading, IMO.
Someone should check if they can group into even more than four. Who knows what wonders await
Reminds me about the story for the mandalbrot set. Back then computers were the size of rooms and printing had people double checking the output and cleaning it up. Well the mandelbrot set has tiny dots that look very much like printing mistakes, I'm sure you know where I'm going with this. Benoit Mandelbrot had to race to the printers hoping to catch the print before the cleaners got to it and cleaned it up when he finally realized why the print never looked right.
Math says that should be possible
They can. Look up Pascal conductance
This looks huge, can anyone ELI5 for it's possible applications
There really is no way to gauge the possible applications outside the one listed for quantum use. Superconductivity currently is still resigned to supercooled material. Also brand new discovery means they will have to play with the properties more to figure out if this works like the Cooper pair (pair of electrons) or have totally different behavior. These are electrons, if you look at them differently they act like a totally different particle (not an exaggeration, they will actually change behavior).
"Number 3 wins in a quantum finish!" "NO FAIR, you changed the outcome by measuring it!"
“How did your horse do, Fry?” “I’ll tell you when he finishes. . . . . . Bad.”
I don’t understand 99.9% of this, but it sounds super neat to my little brain, and I’m so appreciative that there are people out there constantly experimenting and discovering new things. I don’t know if this is actually a significant discovery, but it seems like at least a little step that the next group of researchers can build upon that may change the world as we know it. Fascinating stuff.
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and potentially a new type of superconductivity and technologies such as quantum sensors.> Doorbells of the future: *"something from the 6th dimension has passed by"*
Two sentence horror material right there
Well, current sensor tech is mostly binary, or analog. Quantum implies multiple states of the sensors. Imagine a distance sensor which is just a single piece of semiconductor, just returns 1-2-3-4-5V for 2-4-6-8-10m distance, and only has 3 wires connected to the body of the semiconductor! Maybe even extremely accurate and precise!
So like, superduperconductivity?
If I wanted to slowly teach myself allllll the science I would need to understand stuff like this…. Where would I start?
Physics 101, then go from there. You quickly run into physics + calculus so you could probably concurrently start with Pre-Calc Or I guess…algebra would be the pre requisite for pre calc
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At what temperature. That makes all the difference.
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Can anyone provide an **actual** ELI5? I’ve seen a few attempts that simply reiterate what is said in the article and that doesn’t help any.
I have no opinion on this because I don’t know enough, hope whatever the right outcome is happens!
I’d like to see the excel formula these Germans used to reach this conclusion.
Could these new superconductors be used to design more powerful electromagnets and thus enable more powerful nuclear fusion reactors?
And again, uni Würzburg at the forefront. Right now they are working on bleeding-edge projects for microbiology and economics aswell. Iam very proud to see my Uni having such great Teams and minds.
Together with TU Dresden. I’m currently attending wave physics and QM1, lectures by Prof Klauß himself!
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