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Superconductors have a current limit above which they are no longer superconductors. It is possible that a room temperature superconductor could be created tha

Superconductors have a current limit above which they are no longer superconductors. It is possible that a room temperature superconductor could be created that has a limit too low to be of any practical use. It seems this is worth cautious excitement, but don't get too excited yet.

prewett 3y ago
The abstract says that T_c is 127 C, which should be comfortably above room temperature for most of the planet
- quux 3y ago
  For now...
- jacquesm 3y ago
  GP is talking about the current density rather than the temperature.
tux3 3y ago
Couldn't we make really thick wires to increase the current limit :) ? After all, there's no need for expensive cooling and the material looks reasonably cheap! (assuming it's real, of course..)
- jacquesm 3y ago
  Let's wait to see what the maximum number of A/cm^2 is before determining if that is even necessary. It's possible that they already normalized the figure, and if that's the case then 125 mA/cm^2 would be 'bad news' in the sense that even though the temperature and pressure are much better than other superconductors the critical current is much, much worse. But given the way the paper is formulated I'm not sure if that is a proper reading and it is very well possible that they are talking about a particular thin film sample (which would make it a small fraction of a square centimeter in cross section) and how much current they passed through that sample. In which case the situation would be much better already, especially if it turns out that the sample was extremely thin and/or narrow. Too early to tell without more information.
jychang 3y ago
250mA at 25 Celsius, according to the paper
- jacquesm 3y ago
  That needs another element, the cross section of the conductor otherwise it is meaningless.
- colechristensen 3y ago
  Oof, all right then. Perhaps there's room for improvement, but there would need to be a lot before this is useful/competitive even in lab settings. For comparison, high temperature superconductors (in this context high temperature means tens of degrees kelvin) like the recently rather revolutionary ReBCO has critical current values measured in hundreds of thousands of amps per square centimeter. That would be a factor of a million.
  - jacquesm 3y ago
    It's a thin film according to the article linked, but there is no mention of how thin it is (it could be a monolayer) and there is no mention of how wide the film was so the 250 mA figure can not be used to determine whether or not there is 'room for improvement' or even a necessity for that (unless it was already normalized, for which I see no evidence). The 'Critical current' isn't mentioned at all in terms of the cross section of the conductor, just as a function of temperature and magnetic flux which they really should have provided to be able to make sense of the figure. ReBCO is 8 MA / cm^2 (that's million, not milli), the thin film layer they tested with could well be so thin that it is in the same ballpark or it could be a small fraction. This is clearly a very early result and until they have more insight into how it works (assuming it really works...) we'll have to be patient before we get more meaningful figures on the actual current carrying capacity of thicker conductors made out of this stuff. They were happy enough to be able to prove superconductivity at room temperature and normal pressure, clearly they are still a ways away from being able to line up a comparison with ReBCO with respect to current density. But surely that will happen soon if this is real.

prewett 3y ago

The abstract says that T_c is 127 C, which should be comfortably above room temperature for most of the planet

quux 3y ago
For now...
jacquesm 3y ago
GP is talking about the current density rather than the temperature.

tux3 3y ago

Couldn't we make really thick wires to increase the current limit :) ? After all, there's no need for expensive cooling and the material looks reasonably cheap! (assuming it's real, of course..)

jacquesm 3y ago
Let's wait to see what the maximum number of A/cm^2 is before determining if that is even necessary. It's possible that they already normalized the figure, and if that's the case then 125 mA/cm^2 would be 'bad news' in the sense that even though the temperature and pressure are much better than other superconductors the critical current is much, much worse. But given the way the paper is formulated I'm not sure if that is a proper reading and it is very well possible that they are talking about a particular thin film sample (which would make it a small fraction of a square centimeter in cross section) and how much current they passed through that sample. In which case the situation would be much better already, especially if it turns out that the sample was extremely thin and/or narrow. Too early to tell without more information.

jychang 3y ago

250mA at 25 Celsius, according to the paper

jacquesm 3y ago
That needs another element, the cross section of the conductor otherwise it is meaningless.
colechristensen 3y ago
Oof, all right then. Perhaps there's room for improvement, but there would need to be a lot before this is useful/competitive even in lab settings. For comparison, high temperature superconductors (in this context high temperature means tens of degrees kelvin) like the recently rather revolutionary ReBCO has critical current values measured in hundreds of thousands of amps per square centimeter. That would be a factor of a million.
- jacquesm 3y ago
  It's a thin film according to the article linked, but there is no mention of how thin it is (it could be a monolayer) and there is no mention of how wide the film was so the 250 mA figure can not be used to determine whether or not there is 'room for improvement' or even a necessity for that (unless it was already normalized, for which I see no evidence). The 'Critical current' isn't mentioned at all in terms of the cross section of the conductor, just as a function of temperature and magnetic flux which they really should have provided to be able to make sense of the figure. ReBCO is 8 MA / cm^2 (that's million, not milli), the thin film layer they tested with could well be so thin that it is in the same ballpark or it could be a small fraction. This is clearly a very early result and until they have more insight into how it works (assuming it really works...) we'll have to be patient before we get more meaningful figures on the actual current carrying capacity of thicker conductors made out of this stuff. They were happy enough to be able to prove superconductivity at room temperature and normal pressure, clearly they are still a ways away from being able to line up a comparison with ReBCO with respect to current density. But surely that will happen soon if this is real.