5 ms·

The superconductivity of layered graphene

134 points by westurner 2y ago

PaulRobinson 2y ago
I think everything we don't have a model for is surprisingly strange. Gravity only seems "normal" because we've been teaching a reasonable model for it for hundreds of years - Aristotle thought things fell to the ground because that was "their nature", but thought it quite weird. X-Rays seem bonkers unless you've grown up with them, and there is something deeply unnerving about genetics, quantum and even GenAI until you've spent some time pulling apart the innards and building an explainable model that makes sense to you. And even then it can catch you out. More ways to explain the models help normalise it all - what's now taught at 9th grade used to be advanced post-doc research, in almost every field. And so it goes on. 2D superconductors don't make much sense because, as the article says, theory is behind experimentation here. That's also why there is both incredible excitement, but also a worry that none of this is going to stack up to anything more than a bubble. My old Uni (Manchester) doubled down hard on the work of Geim and Novoselov by building a dedicated "Graphene Institute", after they got the Nobel Prize, but even 15 years after that award most people are still trying to figure out what does it all actually mean really? Not just in terms of the theory of physics, but how useful is this stuff, in real world usage? It'll settle down in due course. The model will become apparent, we'll be able to explain it through a series of bouncing back between theory and experiment, as ever, and then it won't seem so strange any more. I'm not sure that'll ever be true of quantum computing for me, but then I am getting a bit older now...
- ggddv 2y ago
  It’s interesting to think what in people’s personal perception makes them find strange thing interesting or scary or boring. Especially when it comes to grapheme.
  - desdenova 2y ago
    Imagine doing computing on grapheme clusters.
    - HappMacDonald 2y ago
      That's what I thought LLMs did
- aaronblohowiak 2y ago
  I still don’t believe explanations for gravity…let alone dark matter!
  - hansvm 2y ago
    Not believing an explanation for dark matter seems prudent. It's just the name we've given to a certain set of observations not matching how we believe the universe works. We're still piecing together the details.
  - moffkalast 2y ago
    Relevant xkcd tooltip: https://xkcd.com/1489 https://xkcd.com/1489
  - __MatrixMan__ 2y ago
    Do you suppose everything is explainable? Gravity feels to me like the sort of thing that just sort of is. I'm all for better characterizations of it, but I'm not holding my breath for an answer to: why?
    - jepj57 2y ago
      Everything may be explainable, just not by humanity. How does our biology affect the limits of what we can comprehend?
      - __MatrixMan__ 2y ago
        Oh plenty of ways probably. I expect there are perspectives out there which would have a look at our biggest questions and find them to be mundane with obvious answers but which would themselves boggle at concepts that we consider elementary. But here I am in this body, and not that one, so I'm content to accept an axiom or two.
    - aaronblohowiak 2y ago
      the question is depth and quality of explainability as determined by the predictive power those explanations provide...
- SecretDreams 2y ago
  > My old Uni (Manchester) doubled down hard on the work of Geim and Novoselov by building a dedicated "Graphene Institute", after they got the Nobel Prize, but even 15 years after that award most people are still trying to figure out what does it all actually mean really? Not just in terms of the theory of physics, but how useful is this stuff, in real world usage? That's the beauty of real research. There's no guarantees it'll pan out. But it's generally worth doing and spending (sometimes decades of) time exploring. Too many people have become infatuated with instant gratification. It's pervasive even in young, scientific minds. The real gratification is failing that same test 100 times until you finally land on a variation that might work. And then figuring out why it worked. Edit: And if that success never comes, the gratification is graduating and moving on to more solvable problems, but bringing with you the scientific methods you learned along the way. Scientists might spend their whole lives working on something that won't work and that's okay. If that isn't for you, go into product dev.
- tasty_freeze 2y ago
  When I was a kid, magnets seemed magical. I'm 60 now, and they still seem like magic, despite always having some on hand to play with.
  - Synaesthesia 2y ago
    Magnets, how do they work? It's surprisingly complicated actually!
    - pelagicAustral 2y ago
      Miracles!
dr_dshiv 2y ago
My interest with these overlapping lattices is the creation of fractional electric charges (Hall effect) and through, essentially, Moiré patterns. The angle of alignment will make a big effect. Let me make an artifact to demonstrate… brb
- spiritplumber 2y ago
  It reminded me of a DOOM glitch that you get with a zero-width wall.
  - HappMacDonald 2y ago
    I'm curious what glitch you mean, maybe you can find a link describing it? All of my googling just turns up arbitrary problems that often end up being due to poorly authored maps. :)
    - spiritplumber 2y ago
      https://doomwiki.org/wiki/Moir%C3%A9_error https://doomwiki.org/wiki/Moir%C3%A9_error
- dr_dshiv 2y ago
  https://claude.site/artifacts/f024844e-73c2-4eb1-afc9-401f3dea9bcf https://claude.site/artifacts/f024844e-73c2-4eb1-afc9-401f3d... Here you go. See how there are different densities and geometries at different angles. These lattice overlays can create fractional electrical charges — which is very strange — but how this affects super conductivity is unclear.
  - CamperBob2 2y ago
    Very cool example!
benbini 2y ago
This is exciting, sounds like new theory incoming (or possible way to test existing string/other theories?). I'd love to see PBS Spacetime or some other credible outlet explain the details of the experiment / implications for mere mortals.
quantumtwist 2y ago
Physicist here. The superconductivity in layered graphene is indeed surprisingly strange, but this popular article may not do it justice. Here are some older articles on the same topic that may be more informative: https://www.quantamagazine.org/how-twisted-graphene-became-the-big-thing-in-physics-20190430/ https://www.quantamagazine.org/how-twisted-graphene-became-t..., https://www.quantamagazine.org/a-new-twist-reveals-superconductivitys-secrets-20210316/ https://www.quantamagazine.org/a-new-twist-reveals-supercond.... Let me briefly say why some reasons this topic is so interesting. Electrons in a crystal always have both potential energy (electrical repulsion) and kinetic energy (set by the atomic positions and orbitals). The standard BCS theory of superconductivity only works well when the potential energy is negligible, but the most interesting superconductors --- probably including all high temperature ones like the cuprates --- are in the regime where potential energy is much stronger than kinetic energy. These are often in the class of "unconventional" superconductors where vanilla BCS theory does not apply. The superconductors in layered (and usually twisted) graphene lie in that same regime of large potential/kinetic energy. However, their 2d nature makes many types of measurements (and some types of theories) much easier. These materials might be the best candidate available to study to get a handle on how unconventional superconductivity "really works". (Besides superconductors, these same materials have oodles of other interesting phases of matter, many of which are quite exotic.)
- bryan0 2y ago
  Thank you for the additional info and links. This is why I love HN comments
- bilsbie 2y ago
  While we have you, have any new theories or avenues of research come out of the lk99 stuff or was it completely just hype and known physics?
- java-man 2y ago
  BCS == Bardeen–Cooper–Schrieffer [0]. [0] https://en.wikipedia.org/wiki/BCS_theory https://en.wikipedia.org/wiki/BCS_theory
- tagrun 2y ago
adrian_b 2y ago
Slightly different preprint variants: https://arxiv.org/abs/2406.13742 https://arxiv.org/abs/2406.13742 https://arxiv.org/abs/2406.13740v2 https://arxiv.org/abs/2406.13740v2
unit149 2y ago
[dead]
jnurmine 2y ago
Is this exactly 1.1 degrees? Or is it 1.09955742876? What I mean -- did they round up, is there some connection to universal constants? Edit: I don't understand where the 1.1 degrees comes from. Why is it 1.1 and not something else...
- zamadatix 2y ago
  It's not exactly a single ultra-specific 1.1000000... degree value only, just values approximately close to that. As to what the connection is: that's what the research is trying to unearth more about.

134 points by westurner 2y ago

I think everything we don't have a model for is surprisingly strange. Gravity only seems "normal" because we've been teaching a reasonable model for it for hundreds of years - Aristotle thought things fell to the ground because that was "their nature", but thought it quite weird. X-Rays seem bonkers unless you've grown up with them, and there is something deeply unnerving about genetics, quantum and even GenAI until you've spent some time pulling apart the innards and building an explainable model that makes sense to you. And even then it can catch you out. More ways to explain the models help normalise it all - what's now taught at 9th grade used to be advanced post-doc research, in almost every field. And so it goes on. 2D superconductors don't make much sense because, as the article says, theory is behind experimentation here. That's also why there is both incredible excitement, but also a worry that none of this is going to stack up to anything more than a bubble. My old Uni (Manchester) doubled down hard on the work of Geim and Novoselov by building a dedicated "Graphene Institute", after they got the Nobel Prize, but even 15 years after that award most people are still trying to figure out what does it all actually mean really? Not just in terms of the theory of physics, but how useful is this stuff, in real world usage? It'll settle down in due course. The model will become apparent, we'll be able to explain it through a series of bouncing back between theory and experiment, as ever, and then it won't seem so strange any more. I'm not sure that'll ever be true of quantum computing for me, but then I am getting a bit older now...

ggddv 2y ago
It’s interesting to think what in people’s personal perception makes them find strange thing interesting or scary or boring. Especially when it comes to grapheme.
- desdenova 2y ago
  Imagine doing computing on grapheme clusters.
  - HappMacDonald 2y ago
    That's what I thought LLMs did
aaronblohowiak 2y ago
I still don’t believe explanations for gravity…let alone dark matter!
- hansvm 2y ago
  Not believing an explanation for dark matter seems prudent. It's just the name we've given to a certain set of observations not matching how we believe the universe works. We're still piecing together the details.
- moffkalast 2y ago
  Relevant xkcd tooltip: https://xkcd.com/1489 https://xkcd.com/1489
- __MatrixMan__ 2y ago
  Do you suppose everything is explainable? Gravity feels to me like the sort of thing that just sort of is. I'm all for better characterizations of it, but I'm not holding my breath for an answer to: why?
  - jepj57 2y ago
    Everything may be explainable, just not by humanity. How does our biology affect the limits of what we can comprehend?
    - __MatrixMan__ 2y ago
      Oh plenty of ways probably. I expect there are perspectives out there which would have a look at our biggest questions and find them to be mundane with obvious answers but which would themselves boggle at concepts that we consider elementary. But here I am in this body, and not that one, so I'm content to accept an axiom or two.
  - aaronblohowiak 2y ago
    the question is depth and quality of explainability as determined by the predictive power those explanations provide...
SecretDreams 2y ago
> My old Uni (Manchester) doubled down hard on the work of Geim and Novoselov by building a dedicated "Graphene Institute", after they got the Nobel Prize, but even 15 years after that award most people are still trying to figure out what does it all actually mean really? Not just in terms of the theory of physics, but how useful is this stuff, in real world usage? That's the beauty of real research. There's no guarantees it'll pan out. But it's generally worth doing and spending (sometimes decades of) time exploring. Too many people have become infatuated with instant gratification. It's pervasive even in young, scientific minds. The real gratification is failing that same test 100 times until you finally land on a variation that might work. And then figuring out why it worked. Edit: And if that success never comes, the gratification is graduating and moving on to more solvable problems, but bringing with you the scientific methods you learned along the way. Scientists might spend their whole lives working on something that won't work and that's okay. If that isn't for you, go into product dev.
tasty_freeze 2y ago
When I was a kid, magnets seemed magical. I'm 60 now, and they still seem like magic, despite always having some on hand to play with.
- Synaesthesia 2y ago
  Magnets, how do they work? It's surprisingly complicated actually!
  - pelagicAustral 2y ago
    Miracles!

dr_dshiv 2y ago

My interest with these overlapping lattices is the creation of fractional electric charges (Hall effect) and through, essentially, Moiré patterns. The angle of alignment will make a big effect. Let me make an artifact to demonstrate… brb

spiritplumber 2y ago
It reminded me of a DOOM glitch that you get with a zero-width wall.
- HappMacDonald 2y ago
  I'm curious what glitch you mean, maybe you can find a link describing it? All of my googling just turns up arbitrary problems that often end up being due to poorly authored maps. :)
  - spiritplumber 2y ago
    https://doomwiki.org/wiki/Moir%C3%A9_error https://doomwiki.org/wiki/Moir%C3%A9_error
dr_dshiv 2y ago
https://claude.site/artifacts/f024844e-73c2-4eb1-afc9-401f3dea9bcf https://claude.site/artifacts/f024844e-73c2-4eb1-afc9-401f3d... Here you go. See how there are different densities and geometries at different angles. These lattice overlays can create fractional electrical charges — which is very strange — but how this affects super conductivity is unclear.
- CamperBob2 2y ago
  Very cool example!

benbini 2y ago

This is exciting, sounds like new theory incoming (or possible way to test existing string/other theories?). I'd love to see PBS Spacetime or some other credible outlet explain the details of the experiment / implications for mere mortals.

quantumtwist 2y ago

Physicist here. The superconductivity in layered graphene is indeed surprisingly strange, but this popular article may not do it justice. Here are some older articles on the same topic that may be more informative: https://www.quantamagazine.org/how-twisted-graphene-became-the-big-thing-in-physics-20190430/ https://www.quantamagazine.org/how-twisted-graphene-became-t..., https://www.quantamagazine.org/a-new-twist-reveals-superconductivitys-secrets-20210316/ https://www.quantamagazine.org/a-new-twist-reveals-supercond.... Let me briefly say why some reasons this topic is so interesting. Electrons in a crystal always have both potential energy (electrical repulsion) and kinetic energy (set by the atomic positions and orbitals). The standard BCS theory of superconductivity only works well when the potential energy is negligible, but the most interesting superconductors --- probably including all high temperature ones like the cuprates --- are in the regime where potential energy is much stronger than kinetic energy. These are often in the class of "unconventional" superconductors where vanilla BCS theory does not apply. The superconductors in layered (and usually twisted) graphene lie in that same regime of large potential/kinetic energy. However, their 2d nature makes many types of measurements (and some types of theories) much easier. These materials might be the best candidate available to study to get a handle on how unconventional superconductivity "really works". (Besides superconductors, these same materials have oodles of other interesting phases of matter, many of which are quite exotic.)

bryan0 2y ago
Thank you for the additional info and links. This is why I love HN comments
bilsbie 2y ago
While we have you, have any new theories or avenues of research come out of the lk99 stuff or was it completely just hype and known physics?
java-man 2y ago
BCS == Bardeen–Cooper–Schrieffer [0]. [0] https://en.wikipedia.org/wiki/BCS_theory https://en.wikipedia.org/wiki/BCS_theory
tagrun 2y ago

adrian_b 2y ago

Slightly different preprint variants: https://arxiv.org/abs/2406.13742 https://arxiv.org/abs/2406.13742 https://arxiv.org/abs/2406.13740v2 https://arxiv.org/abs/2406.13740v2

unit149 2y ago

[dead]

jnurmine 2y ago

Is this exactly 1.1 degrees? Or is it 1.09955742876? What I mean -- did they round up, is there some connection to universal constants? Edit: I don't understand where the 1.1 degrees comes from. Why is it 1.1 and not something else...

zamadatix 2y ago
It's not exactly a single ultra-specific 1.1000000... degree value only, just values approximately close to that. As to what the connection is: that's what the research is trying to unearth more about.