5 ms·

Honestly I don't see anything that would prove superconductivity in this video. If LK-99 is a type-II superconductor you should observe flux pinning i.e. you wo

Honestly I don't see anything that would prove superconductivity in this video. If LK-99 is a type-II superconductor you should observe flux pinning i.e. you would be able to move the flake with a tweezer and it would be stuck in place as the magnetic flux lines are pinned to defects in the material. I haven't seen any details on the supposed properties of the material like the coherence length, but from the original paper it seems the critical field of a small flake is rather low at a few 100-1000 Oe, so a more convincing test than thermal cycling would be to simply use an electromagnet and increase the field strength, the sample should then drop once the (second) critical field is reached. If the critical field strength is too high you can reduce it by heating the sample, but what's critical is to observe breakdown of diamagnetism with an increase in field strength without any form of hysteresis, which you won't observe in the same way in a diamagnet. The best test would probably be to produce a Josephson junction and measure Shapiro steps at high frequency, that's something that cannot be explained by anything except a superconducting quantum material. As the sample is highly impure it could even be enough to irradiate it with a microwave source and measure the reflectivity / transmittance, there could even be intrinsic Josephson effect like in high Tc superconductors. Impossible to say though without knowing more details about the material.

floxy 3y ago
There have been some people saying that LK-99 might only be superconducting in one dimension. Does anyone know how that (or even just 2-D/planar superconductivity) would effect the levitation of samples? For the 1-D case, maybe there would be issues in creating loops in the bulk material for persistent currents to flow in? It might be hard to make a Josephson junction unless you knew the orientation of the superconductivity direction? Has anybody studied this before? My intuition breaks down here.
- ThePhysicist 3y ago
  The superconducting wave function can have different symmetry, e.g. most/all low-temperature superconductors have s-wave symmetry (meaning the wave function amplitude is the same in all directions), whereas high-temperature superconductors have d-wave symmetry, which means the wave function amplitude has lobes and drops to zero along the diagonal axes. There are no p-wave superconductors to my knowledge (which I guess is meant when they talk about a 1D superconductor, i.e. the wave function has p-symmetry, but not even sure if that's what they mean). I know the main researcher has brought forward a modified BCS theory that combines insulator-metal transition physics with superconductivity, no idea though what to make of that.
  - marcosdumay 3y ago
    > which I guess is meant when they talk about a 1D superconductor, i.e. the wave function has p-symmetry, but not even sure if that's what they mean I think they mean it only appears on islands that are much longer than they are wide or high. I.E. I understand it as a geometric limitation on the form of the crystals they can make. The theoretical stuff that got here implies it has d-wave symmetry, and so does the original paper.
marklubi 3y ago
[flagged]
- jjoonathan 3y ago
  Theranos raised $724 million using intentional deception. LK99 is an incomplete paper that someone posted to arXiv.
  - marklubi 3y ago
    My comment had nothing to do about the money that Theranos raised, but about how the hype feels. Theranos was sooooo hyped on HN early on, and now we know how it turned out. This feels like practically a carbon copy of that hype.
    - jjoonathan 3y ago
      All hype cycles look like this. If Theranos was the last one you witnessed, I envy your ability to unplug.
    - stephenitis 3y ago
      The hype is more warranted here because I think material and physics scientists are excited and publicly and clearly skeptical. There is a wider knowledge that this may be nothing or somewhere in between. The rollercoaster following the developments is why the wider public is enjoying following it as science entertainment. On Twitter it seems like crypto bros are trying to scam with a LK-99 coin. AI/ML crowd is pondering what happens to computing power in 5-10-15 years if LK-99 is proven applicable to advance current technologies. There is a large mix of aspirational futurism and a lot of tempered real science going on here. All in real time, on active, Twitter, WeChat/Billibili(?) etc
      - SubiculumCode 3y ago
        a decent crypto strat is to buy a coin named after a major news event asap, then sell within a day
deleted 3y ago
[deleted]
carabiner 3y ago
Damn. It's over.
deleted 3y ago
[deleted]
pnwcoder 3y ago
What would be an explanation for the partial levitation of the LK-99 sample shown in the video?
- ThePhysicist 3y ago
  Could be normal diamagnetism, or even ferromagnetism. Very hard to say as they don't even give any field strengths in the video, it's just a Neodym magnet they hold near the sample. If I understand the video correctly they just orient the magnet by hand, so I would not even rule out a ferromagnetic effect. There can be multiple regions with different orientation in such a polycristalline material, which can produce all kinds of weird effects. Not saying that it's not a superconductor, just that I would not draw any conclusions from this video. If this was a type-II superconductor and the flux pinning is strong enough to lift the flake up you should be able to drag it across the bottom of the beaker with the magnet as the magnetic flux lines "impale" the crystal, i.e. they are in an energy minimum and moving them out of there causes resistance as they need to break the superconductivity in the material surrounding the defect where they are pinned. If it's just diamagnetism that's not the case. So observing that the flake is completely stationary when the magnet is moved in our out tells me this likely isn't flux pinning we're seeing. I'm a bit skeptical how they even know it's the right material, getting the doping right seemed quite intricate so it would seem quite extraordinary that they can hit the right process after trying for a few days. Not saying they didn't, but so far I'm rather inclined to believe they just got a ferromagnetic metal flake (which is easy to get following the thermal annealing process they did, or even by banging the material up a bit as they seem to have done for getting it out of the synthesis tubes).
  - lr1970 3y ago
    > Could be normal diamagnetism, or even ferromagnetism. I am curious how one could confuse the two? One leads to repulsion, another to attraction.
    - ThePhysicist 3y ago
      I'm not even sure they reversed the magnet polarity in this video, it seems they just removed the magnet and put it back, so there's no way to rule out a ferromagnetic effect. Again, I just find it really hard to deduce anything from this footage, not saying it can't be a superconductor. I'm not even sure they reversed the magnet polarity in this video, it seems they just removed the magnet and put it back, so there's no way to rule out a ferromagnetic effect. I'm not sure either if LK-99 is a type-II superconductor but I would believe so given the papers I've read. Type-II superconductors aren't perfect diamagnets, they allow magnetic flux to penetrate the superconductor once you hit the first critical field, these flux vortices then get pinned at sites of defects where the energy requirement for breaking the superconductivity is lowest. That's what keeps a type-II superconductor levitating over a magnet, a type I superconductor or perfect diamagnet wouldn't do that. Then again I have never seen how e.g. a tiny YBCO flake (high Tc type-II superconductor) would behave if you put it in a beaker and dragged a Neodym magnet below it, so who knows.

floxy 3y ago

There have been some people saying that LK-99 might only be superconducting in one dimension. Does anyone know how that (or even just 2-D/planar superconductivity) would effect the levitation of samples? For the 1-D case, maybe there would be issues in creating loops in the bulk material for persistent currents to flow in? It might be hard to make a Josephson junction unless you knew the orientation of the superconductivity direction? Has anybody studied this before? My intuition breaks down here.

ThePhysicist 3y ago
The superconducting wave function can have different symmetry, e.g. most/all low-temperature superconductors have s-wave symmetry (meaning the wave function amplitude is the same in all directions), whereas high-temperature superconductors have d-wave symmetry, which means the wave function amplitude has lobes and drops to zero along the diagonal axes. There are no p-wave superconductors to my knowledge (which I guess is meant when they talk about a 1D superconductor, i.e. the wave function has p-symmetry, but not even sure if that's what they mean). I know the main researcher has brought forward a modified BCS theory that combines insulator-metal transition physics with superconductivity, no idea though what to make of that.
- marcosdumay 3y ago
  > which I guess is meant when they talk about a 1D superconductor, i.e. the wave function has p-symmetry, but not even sure if that's what they mean I think they mean it only appears on islands that are much longer than they are wide or high. I.E. I understand it as a geometric limitation on the form of the crystals they can make. The theoretical stuff that got here implies it has d-wave symmetry, and so does the original paper.

marklubi 3y ago

[flagged]

jjoonathan 3y ago
Theranos raised $724 million using intentional deception. LK99 is an incomplete paper that someone posted to arXiv.
- marklubi 3y ago
  My comment had nothing to do about the money that Theranos raised, but about how the hype feels. Theranos was sooooo hyped on HN early on, and now we know how it turned out. This feels like practically a carbon copy of that hype.
  - jjoonathan 3y ago
    All hype cycles look like this. If Theranos was the last one you witnessed, I envy your ability to unplug.
  - stephenitis 3y ago
    The hype is more warranted here because I think material and physics scientists are excited and publicly and clearly skeptical. There is a wider knowledge that this may be nothing or somewhere in between. The rollercoaster following the developments is why the wider public is enjoying following it as science entertainment. On Twitter it seems like crypto bros are trying to scam with a LK-99 coin. AI/ML crowd is pondering what happens to computing power in 5-10-15 years if LK-99 is proven applicable to advance current technologies. There is a large mix of aspirational futurism and a lot of tempered real science going on here. All in real time, on active, Twitter, WeChat/Billibili(?) etc
    - SubiculumCode 3y ago
      a decent crypto strat is to buy a coin named after a major news event asap, then sell within a day

deleted 3y ago

[deleted]

carabiner 3y ago

Damn. It's over.

deleted 3y ago

[deleted]

pnwcoder 3y ago

What would be an explanation for the partial levitation of the LK-99 sample shown in the video?

ThePhysicist 3y ago
Could be normal diamagnetism, or even ferromagnetism. Very hard to say as they don't even give any field strengths in the video, it's just a Neodym magnet they hold near the sample. If I understand the video correctly they just orient the magnet by hand, so I would not even rule out a ferromagnetic effect. There can be multiple regions with different orientation in such a polycristalline material, which can produce all kinds of weird effects. Not saying that it's not a superconductor, just that I would not draw any conclusions from this video. If this was a type-II superconductor and the flux pinning is strong enough to lift the flake up you should be able to drag it across the bottom of the beaker with the magnet as the magnetic flux lines "impale" the crystal, i.e. they are in an energy minimum and moving them out of there causes resistance as they need to break the superconductivity in the material surrounding the defect where they are pinned. If it's just diamagnetism that's not the case. So observing that the flake is completely stationary when the magnet is moved in our out tells me this likely isn't flux pinning we're seeing. I'm a bit skeptical how they even know it's the right material, getting the doping right seemed quite intricate so it would seem quite extraordinary that they can hit the right process after trying for a few days. Not saying they didn't, but so far I'm rather inclined to believe they just got a ferromagnetic metal flake (which is easy to get following the thermal annealing process they did, or even by banging the material up a bit as they seem to have done for getting it out of the synthesis tubes).
- lr1970 3y ago
  > Could be normal diamagnetism, or even ferromagnetism. I am curious how one could confuse the two? One leads to repulsion, another to attraction.
  - ThePhysicist 3y ago
    I'm not even sure they reversed the magnet polarity in this video, it seems they just removed the magnet and put it back, so there's no way to rule out a ferromagnetic effect. Again, I just find it really hard to deduce anything from this footage, not saying it can't be a superconductor. I'm not even sure they reversed the magnet polarity in this video, it seems they just removed the magnet and put it back, so there's no way to rule out a ferromagnetic effect. I'm not sure either if LK-99 is a type-II superconductor but I would believe so given the papers I've read. Type-II superconductors aren't perfect diamagnets, they allow magnetic flux to penetrate the superconductor once you hit the first critical field, these flux vortices then get pinned at sites of defects where the energy requirement for breaking the superconductivity is lowest. That's what keeps a type-II superconductor levitating over a magnet, a type I superconductor or perfect diamagnet wouldn't do that. Then again I have never seen how e.g. a tiny YBCO flake (high Tc type-II superconductor) would behave if you put it in a beaker and dragged a Neodym magnet below it, so who knows.