Physicists May Be One Step Closer To Explaining High-Temp Superconductivity 58
sciencehabit writes For years some physicists have been hoping to crack the mystery of high-temperature superconductivity—the ability of some complex materials to carry electricity without resistance at temperatures high above absolute zero—by simulating crystals with patterns of laser light and individual atoms. Now, a team has taken—almost—the next-to-last step in such 'optical lattice' simulation by reproducing the pattern of magnetism seen in high-temperature superconductors from which the resistance-free flow of electricity emerges.
Relatively high temp... (Score:1, Redundant)
So when they talk about high temp semiconductors, it is still around -211F
What does this mean in practical terms?
Is this an easy temperature to maintain?
What techniques or materials could we use to keep that temp?
How does power generation and pulling off waste heat factor into it?
I look at all the heat handlers in a datacenter and wonder, ok what if we step this down a couple hundred degrees
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superconductors, not semiconductors, genius.
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Actually, 138 K
Re:Relatively high temp... (Score:5, Informative)
138K = -211F
The key threshold is 77K. Above that, and you can cool with liquid nitrogen. A liter of liquid N2 costs less than a liter of milk. A liter of liquid helium costs about a hundred times as much.
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Does this make the proposed superconducting power transmission corridors feasible?
http://en.wikipedia.org/wiki/E... [wikipedia.org]
Has anybody proposed a time-to-market for this, or are we still in the infinite loop of '20 years from now'?
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Re:Relatively high temp... (Score:5, Insightful)
Superconductive materials have 0 resistance which means there is no energy lost to heat.
As for how easy these temperatures are to hold, see your local hospital and ask them how easy it is for them to maintain their MRI machine's superconductive magnets.
What understanding the underlying properties of super conductive materials allows is for us to perhaps engineer some meta-materials that hold such properties at room temperature.
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Re:Relatively high temp... (Score:4, Informative)
You will always have heat buildup to deal with in any system that does something useful.
Superconducting magnets are useful, even if they're not doing work.
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Um, yeah, that's what they do in MRIs. Only have to energize it and keep it cool. They get really ticked if they have to turn it off - very time consuming and expensive to turn it back on again.
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Remember the assumptions [subbot.org] of Thermodynamics?
The System is continuous. There are no scale, quantum, or relativistic effects.
The laws of thermodynamics are relevant only within a narrow range of physical phenomena, which we have gotten out of.
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And then the "Laws" turn out to be more like suggestions. Fluctuation theorem...
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The System is continuous. There are no scale, quantum, or relativistic effects.
Utter rubbish, laddie, quite like that image you linked to. Modern thermodynamics has no such limitations. Go look up negative temperature (hint: you might have heard of such things as lasers) for a fun, discrete, quantum thermodynamic system. Heck, Planck's black body radiation was a nice, discrete, quantum thermodynamic system. Ye might want to resort to a teacher that's been around at some point during the last century or so, next time you argue thermodynamics. Such a one might point you towards such thi
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Re:Relatively high temp... (Score:4, Informative)
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Expensive and difficult are different.
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138 K is -211 F
According to the omniscient wiki
http://en.wikipedia.org/wiki/S... [wikipedia.org]
Either liquid He or two stage mechanical coolers are used to get the superconducting magnet down to 77 K
They also note that He is in short supply
So, these new materials, which seem to be able to operate at about twice the temperature of current superconductors (thanks AC above for pointing out mistake)
What does than mean in terms of cost, maintainability and overall benefit of keeping something at 138 K as opposed to 77 K?
Does i
Re:Relatively high temp... (Score:5, Insightful)
I think you may have misread a bit - cheap liquid nitrogen boils at 77K, making it ideal for pre-cooling/outer jacket cooling. Most superconductors on the other hand only work their magic at substantially colder temperatures, which require much more expensive liquid helium cooling (liquid He is 100s of times more expensive, as I recall).
High temperature superconductors are those which operate at temperatures above 30K, with the highest I could find reference to operating at 138K - a range which could easily operate with only liquid nitrogen cooling. Such materials start to open the door to realistic superconducting power distribution, etc, but only in a few very specific cases - it's still radically more expensive than normal conductive wire after all. If we manage another 100K or so jump in superconducting temperature we'd start to get into the range of more traditional cooling systems, even if it's still well below freezing (273.15K). At that point the costs for cooling drop enough that superconductors would start to be attractive for a much wider range of applications.
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I believe one of the reasons liquid nitrogen is a preferred cooling liquid is that it's chemically inert. Do they even sell liquid air? I've never heard of it. I would suspect liquid oxygen might be nastily corrosive, and quite possibly explosive since it will likely boil out of solution before most the rest.
Ah yes, quite. From Wikipedia:
Liquid oxygen is also a very powerful oxidizing agent: organic materials will burn rapidly and energetically in liquid oxygen. Further, if soaked in liquid oxygen, some materials such as coal briquettes, carbon black, etc., can detonate unpredictably from sources of ignition such as flames, sparks or impact from light blows. Petrochemicals, including asphalt, often exhibit this behavior.
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Still 77k, but it's much cooler.
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Hmm... I suppose if you were in a polar orbit, whose plane was being gradually rotated to stay perpendicular to the sun, you could conceivably keep one side of the cable in perpetual shadow for radiant fins, and heavily mirror the sun-facing side. The photon pressure might generate enough torque to coplicate the issue significantly though. Then again, if you shaped that mirror *just* right, maybe you could get the thing to self-stabilize with its orbit facing the sun, so that near-continuous course correct
Re:Relatively high temp... (Score:5, Interesting)
perhaps engineer some meta-materials that hold such properties at room temperature.
Doesn't even have to be room temperature. Being able to make a MRI machine using liquid nitrogen instead of helium would be a huge win.
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"Doesn't even have to be room temperature.
We need improvements in cooling so we can have a colder 'room'
Especialy in summer. In winter you just open a window.
.
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That woudl be pretty unrelated. If you use Helium and not Nitrogen, its not due to the critical temp but due to Type I or II supercondutivity.
Tcs of Superconductors have been far above liquid Nitrogen for 30 years
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Tcs of Superconductors have been far above liquid Nitrogen for 30 years
Yeah, in brittle ceramic form. Something other than cuprates would be nice, preferably something useful ... and not too reliant on rare earths. That's the whole point of the exercise, bloody CuO plane is weird and it's been hard to study, nevermind to make for industrial applications. So they're trying to simulate it, which is quite cool imo. Personally, I'm still betting on AFM insulator effects over Mott insulator ones, but it remains to be seen.
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True, but last time I read up on this their superconductivity broke down when they carried high currents. They're superconductive enough to be useful, for example making very powerful magnets for NMR machines, but not capable of carrying unlimited current.
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This is what I said, but we should be clear there is zero resistive heating *until* the superconductivity breaks down. There is a critical current above which a superconducting wire ceases to superconduct (for complicated reasons).
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Thanks AC, aside from power transmission, are there other technologies which this would enable such as quantum computing (taking a shot in the dark here)?
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The highest temperature superconductor (HgBa2Ca2Cu3Ox(HBCCO) acts at temperatures at or below -140C (-220F). That is still darn cold. Dry Ice sublimates at -78C. What I would consider practical would be around -5C (which means we have 140C to go). Some would want it to be 25C or higher, but you could run a 'national grid' at -5C where "power pumped in" = "power pumped out" without loss. And it would save I2R losses by boatload. Clearly when you look at the number of chemicals and the structure of what
Re:Relatively high temp... (Score:4, Interesting)
A "low temp" superconductor relies on liquid helium to keep it cool (approx 4K). A 'high temp" superconductor relies on liquid nitrogen to keep it cool (77K).
Liquid nitrogen is stupidly cheap - tons of places use liquid nitrogen for a lot of non-superconducting purposes including packaged food preparation, cooling, experimentation (a lot of "cryo" experiments use liquid nitrogen, including the ever popular frozen rose, frozen banana and other science demonstrations).
In fact, to get rid of a small dewar of liquid nitrogen, it's usually just dumped on the table after the demo is done creating a nice effect. A more controlled evaporation is simply leaving the lid off and letting it boil off naturally.
No one keeps stuff cool by liquifying nitrogen onsite. Instead, they just have Air Liquide and similar companies come by every week or so and top off the cryo tank. The cryo tank provides the supply of liquid nitrogen that's needed for the equipment (MRI machines use it in superconducting magnets). Most labs have it available freely as well.
Liquid helium is much more expensive. Liquid nitrogen is so cheap that having it transported and even any wastage is considered "meh". Hell, schools probably buy way more than they need simply because to make it worthwhile you end up with a huge dewar of it.
It was a joke. Did nobody get that? (Score:2)
"explaining" superconductivity? Hum? "explain" ... get it?
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Must be funnier in German
Physics Question? (Score:1)
If we can get a superconducting magnet in the Lagrange point of Mars, would it deflect the solar winds such that a cone would form around Mars, thereby making an atmosphere feasible in the absence of a global electromagnetic shield?
Would that be a very interesting application of superconductors?
superconductivity origins (Score:1)