3 ms·

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 r

by klyrs 4y ago

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#c1 http://hyperphysics.phy-astr.gsu.edu/hbase/Solids/scbc2.html...

willis936 4y ago
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.
raziel2701 4y ago
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.
- jacobn 4y ago
  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.
- klyrs 4y ago
  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.

by klyrs 4y ago

willis936 4y ago

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.

raziel2701 4y ago

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.

jacobn 4y ago
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.
klyrs 4y ago
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.