[HN Gopher] Physicists discover a "family" of robust, supercondu...
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Physicists discover a "family" of robust, superconducting graphene
structures
Author : filoeleven
Score : 87 points
Date : 2022-07-09 16:17 UTC (6 hours ago)
(HTM) web link (news.mit.edu)
(TXT) w3m dump (news.mit.edu)
| yababa_y wrote:
| Has some high powered algebraist or topologist tried figuring out
| what is happening here mathematically? what structure is
| generated by all possible rotations that we are sampling here?
| multiplied by the many layers, what about nonuniform sheets? i'm
| imagining channels of various shapes on the inside... such a
| simple concept, yet such fascinating machinery for the
| measurements. i feel proud when i get a logic analyzer trace off
| an fpga pin!
| marcosdumay wrote:
| Hum... The article actually says it at some point:
|
| https://en.wikipedia.org/wiki/Moir%C3%A9_pattern
|
| https://everettyou.github.io/2018/05/21/Moire.html
|
| I imagine there's no ELI5 explanation of a flat band from
| condensed matter physics.
| notfed wrote:
| > The findings could serve as a blueprint for designing
| practical, room-temperature superconductors.
|
| Cool, up to what temperature?
|
| > 1.7 kelvin
|
| Ok.
| bastawhiz wrote:
| It seems like graphene production at scale has been a few years
| away for a decade or so now. Is there reasonably a future where
| all these incredible graphene-related technologies come to
| fruition within our lifetimes? Or is this just another cold
| fusion of a technology?
| parkingrift wrote:
| Aluminum was extremely difficult to manufacture before the
| Hall-Heroult process. Only a true pessimist would assume we
| would never solve manufacturing problems with graphene.
| willis936 wrote:
| A few things:
|
| 1. REBCO was discovered in the 80s but took decades to work out
| the kinks in mass production of reliable tapes.
|
| 2. Cold fusion is psuedoscience. These results are real.
| Speculating that a technology be vaporware is a very different
| and weaker claim. How do you know that people will not solve
| the engineering problems preventing mass production? Because it
| wasn't immediately obvious how to do it in the past?
| EarlKing wrote:
| Cold fusion got rebranded as Lattice Confinement Fusion.
| raziel2701 wrote:
| Who knows, the academic research is often focused on finding
| out new physics and relies on hero samples. The many failed
| attempts to solve the engineering challenge of scalability and
| reliability in graphene are not very visible to the world.
| gtsop wrote:
| It is a disgrace to intellect when scientific knowledge comes
| with references to magic (even in quotes). Can't we just say
| "exact", "proper", "special", " specific", "just right"? Why
| magic?
| willis936 wrote:
| The term "magic number" pops up in many domains. Often it's
| because the underlying mechanism that yields the empirical
| result is unknown. If that's the case here then that context
| should not be lost because of a semantics argument.
| DennisP wrote:
| "Magic" doesn't necessarily mean supernatural. Google quotes
| the Oxford English dictionary to include these definitions:
|
| - something that has a delightfully unusual quality.
|
| - very effective in producing results, especially desired ones.
|
| I think those definitions make "magic" a better term in this
| case than any of your alternatives.
| ben_w wrote:
| If I say during a code review that "magic numbers should be
| documented", I expect the other person to know the phrase and
| not think I'm talking about _The Book of the Sacred Magic of
| Abramelin the Mage_.
|
| I expect similar things in other domains.
| jamiek88 wrote:
| Fascinating.
|
| Sadly this still needs to be at super low temperature.
|
| This family of superconductors brings us no closer to to room
| temperature superconductors which would change the world.
| klyrs wrote:
| What's really neat about this result is that they're probing a
| link between the band structure of materials and
| superconductivity. So while no, this isn't at room temperature,
| stacked graphenes provide a controllable family of
| metamaterials that can be probed to learn more precisely the
| conditions for superconductivity. If hot* superconductors
| exist, we'll have a better chance at finding them if we
| understand how superconductivity works.
|
| * we don't need "room temperature" superconductors for room
| temperature operation. Superconductors have a shared budget[1]
| of temperature, current and magnetic field -- if we want these
| so-called superconductors to actually carry current at room
| temperature, room temperature isn't enough!
|
| [1] http://hyperphysics.phy-
| astr.gsu.edu/hbase/Solids/scbc2.html...
| raziel2701 wrote:
| What are you talking about not needing room temperature
| superconductors for room temperature operation?
|
| If at 300 K a material has zero resistance then that material
| will carry current at room temperature.
| klyrs wrote:
| Like I said, there's a shared budget for temperature,
| magnetic field and current. If you're sufficiently close to
| the critical temperature, it only takes a small current to
| "blow the budget" which turns your material back into an
| ordinary conductor/resistor. If you remove the current or
| lower the temperature, there's a nonzero switching time
| before the material will return to its superconducting
| phase.
|
| There are some neat applications of this phenomenon in
| superconducting electronics. Cryotrons use transformers to
| produce large fields from small currents to switch a
| higher-current-capacity line from superconducting to
| normal. N-trons and other "current crowding" devices
| perform a similar trick using currents in a pinched region
| attached to the high current line. I can't remember the
| precise details, but different superconducting films are
| more or less inclined to "localize" the normal-phase region
| induced by local current/heat.
|
| Sadly, those neat devices are apparently quite finnicky
| because switching emits heat into their environment, and
| also depends on temperature of that same environment. As
| far as I know, cryotrons are used for high power
| electromagnets to rapidly and safely dump the energy --
| they don't appear to be useful for superconducting
| computers, for example.
| jacobn wrote:
| You need one that can handle higher than room temperature
| for it to be able to carry meaningful amounts of current at
| room temperature. See the link provided in parent for why
| this is.
| willis936 wrote:
| I think it's difficult to get away from the prospect of a
| practical widespread use of superconductors without active
| cooling. Even if ohmic losses in the superconductors is not
| present: environmental temperatures change, especially in
| uncontrolled (outside, in the sun) environments. Running room
| temperature water adds cost and complexity, but a lot less
| than refrigerant (especially cryogenic).
|
| I think mass produceable room temperature superconductors
| would still reshape the world, even if they still required
| active cooling.
| loufe wrote:
| Thanks for your comment, if they broke the temperature
| requirement that would be BIG news.
| mensetmanusman wrote:
| Higher temperature superconductors are already changing the
| world. Doesn't have to be room temp. Some were used to help an
| MIT project reach >20 Tesla magnetic field, which wasn't
| possible before...
|
| I think a great application for these higher temperature (and
| higher B-field, current) superconductors is reaching higher
| magnetic fields for fusion :)
| RF_Savage wrote:
| Or just MRI machines that can function without the
| increasingly expensive liquid helium.
| marcosdumay wrote:
| The main point I get is that the mechanism for this kind of
| superconductivity can be predicted fairly well on computers.
| That means that if it leads to room temperature
| superconductivity, we have an actual path to get it.
|
| And, also, there is always those old too noisy experiments that
| detected superconductivity on certain grains of graphite on
| temperatures up to 700K... That never gathered enough
| confidence, no matter how many times they were repeated. But
| maybe there's something there.
|
| EDIT: Anyway, the other article on the front-page about this
| experiment explains it much better.
| peter_retief wrote:
| Really, I thought it "was" at room temperature?
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