Room temperature superconductivity: One step closer to the Holy Grail of physics
July 9, 2008Scientists at the University of Cambridge have for the first time identified a key component to unravelling the mystery of room temperature superconductivity, according to a paper published in today's edition of the scientific journal Nature.
The quest for room temperature superconductivity has gripped physics researchers since they saw the possibility more than two decades ago. Materials that could potentially transport electricity with zero loss (resistance) at room temperature hold vast potential; some of the possible applications include a magnetically levitated superfast train, efficient magnetic resonance imaging (MRI), lossless power generators, transformers, and transmission lines, powerful supercomputers, etc.
Unfortunately, scientists have been unable to decipher how copper oxide materials superconduct at extremely cold temperatures (such as that of liquid nitrogen), much less design materials that can superconduct at higher temperatures.
Materials that are known to superconduct at the highest temperatures are, unexpectedly, ceramic insulators that behave as magnets before 'doping' (the method of introducing impurities to a semiconductor to modify its electrical properties). Upon doping charge carriers (holes or electrons) into these parent magnetic insulators, they mysteriously begin to superconduct, i.e. the doped carriers form pairs that carry electricity without loss.
The essential conundrum facing researchers in this area has been: how does a magnet that cannot transport electricity transform into a superconductor that is a perfect conductor of electricity? The Cambridge team have made a significant advance in answering this question.
The researchers have discovered where the charge 'hole' carriers that play a significant role in the superconductivity originate within the electronic structure of copper-oxide superconductors. These findings are particularly important for the next step of deciphering the glue that binds the holes together and determining what enables them to superconduct.
Dr Suchitra E. Sebastian, lead author of the study, commented, "An experimental difficulty in the past has been accessing the underlying microscopics of the system once it begins to superconduct. Superconductivity throws a manner of 'veil' over the system, hiding its inner workings from experimental probes. A major advance has been our use of high magnetic fields, which punch holes through the superconducting shroud, known as vortices - regions where superconductivity is destroyed, through which the underlying electronic structure can be probed.
"We have successfully unearthed for the first time in a high temperature superconductor the location in the electronic structure where 'pockets' of doped hole carriers aggregate. Our experiments have thus made an important advance toward understanding how superconducting pairs form out of these hole pockets."
By determining exactly where the doped holes aggregate in the electronic structure of these superconductors, the researchers have been able to advance understanding in two vital areas:
(1) A direct probe revealing the location and size of pockets of holes is an essential step to determining how these particles stick together to superconduct.
(2) Their experiments have successfully accessed the region betwixt magnetism and superconductivity: when the superconducting veil is partially lifted, their experiments suggest the existence of underlying magnetism which shapes the hole pockets. Interplay between magnetism and superconductivity is therefore indicated - leading to the next question to be addressed.
Do these forms of order compete, with magnetism appearing in the vortex regions where superconductivity is killed, as they suggest? Or do they complement each other by some more intricate mechanism? One possibility they suggest for the coexistence of two very different physical phenomena is that the non-superconducting vortex cores may behave in concert, exhibiting collective magnetism while the rest of the material superconducts.
Source: University of Cambridge
Nov 04, 2009 |
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The Singularity cometh...Praise Science!
Good article too. I hadn't grasped that by its very nature super conducting cannot be probed at the nano level without destroying or altering it. It's intuitively obvious now I think about it.
Here's another approach; if we had a good micro simulation computer model of the material down to the electon cloud level then surely the process could be observed and analysed 'in silica'. That would be one cool PhD project. Of course it would require vast computational power.
According to wikipedia loss was about 7.2% in the USA back in 1995. But it really depends on much and how far in addition to real world conditions.
http://en.wikiped...n#Losses
I can see how this would open up whole new possibilities in everything from transportation to microchips.
"The researchers have discovered where the charge 'hole' carriers that play a significant role in the superconductivity originate within the electronic structure of copper-oxide superconductors".
Such sentence doesn't say very much about progress in understanding.
IMHO the 7.2% power distribution loss on wikipedia is suprisingly low. That means what we use today is 92.8% superconducting. The small gain in efficiency would not justify the cost of upgrade even if high temperature high current superconductors become available.
googleplex, I believe you have something there.
I don't know anything about this but there must be a ton of money being spent on this research just to get back that extra few percent (if that is the correct percentage) that we lose. It doesn't make sense to me either. There must be some other benefits related to achieving superconductivity at room temperature that I just don't know about.
Sure, yeah.... me too. Why is this place so full of nut-cases?
If you want to think of our networks as 92.8% superconducting then remaining 7.2% is not conducting at all...
The biggest promise is not in large scale power transmission but in new technologies it would allow and huge costs savings in areas where we have to use liquid helium and nitrogen now to achieve superconductivity (like MRI, NMR, particle accelerators, etc).
full abstract:
arxiv.org/pdf/physics/0607227
This is just not true. HVDC lines have losses of about 3% per 1000 km. That's a ~10% loss over 2 000 miles.
It's not that you have to situate plants within 200 miles, it's just that utillities make sane choices. Efficiency isn't the problem, it's cost, security and utillity.
I don't see the cost going down with super-conductors, especially not with fragile ceramic materials.
Being dependent on a huge central transmission line from across the continent is a huge security issue; it can throw half the continent into rolling black-outs for days or weeks due to bad weather or any old fool sabotaging the lines in the middle of nowhere. This is not unfixable; build many independent transmission lines across the continent or build local back-up generation that just sits idle for years at a time until it's needed; both are enormously costly propositions.
It's also quite futile; it doesn't help wind and solar power all that much as the weather is highly correlated across areas that can be a significant portion of an entire continent. You're still going to need obscene quantities of storage and back-up generation(your old friends coal and gas). I don't see how you're ever going to be competitive on cost, safety or CO2 emissions with nuclear power.
If people are curious about current SC cable projects, see here:http://www.amsc.c...les.html and http://www.superp...php?p=19 (these are the two leading manufacturers of superconducting cable in the world). There are still relatively tiny losses (~1%) associated with these systems as they still need to be cooled.
Soylent, no one is suggesting replacing ALL power lines with one big one. Seriously, where did you get that one from. Redundancy will always be a hallmark of large scale infrastructure. Superconducting lines will be able to help alleviate alot of brownout events because they will allow for other generation facilities in the country to help provide power. Current power generation is only limited to 200-400 miles in the United States (based off of a conversation I've had with DOE officials) due to losses from copper. There is no large scale AC to DC to AC conversion in the US that I have ever heard of. If you could provide information on this (beyond Edison loosing big time on the whole concept), I'd be interested.
Also, googleplex, the superconducting transition is based off of current density. Actually, all materials will eventually break down if you pass too much current through them (though it's usually becuase you heat them up due to internal resistance, which increases with temperature i.e. it will cascade at higher currents. This is contrasted with SCs killing themselves by generating their own internal magnetic field to expel the generated magnetic field from electron movement and therby breaking the cooper pairs, which will coincidentally result in a VERY rapid temperature change afterwards when the SC "quenches" and will often BOIL itself when it goes resistive). I've personally seen (by running the experiment) a 1 um by 100 um cross-section of superconducting film carry 10 Amps of current. To put this in perspective, this correlates to 200 Amps if the 1 um film is 1 cm in width (aka Amps/cm-width). This level is where American Supercondutor was producing 2-3 years ago on the small scale. Now they are producing better than this on larger scales of ~270 A/cm-width at 70 meters of continous length(see http://www.amsc.c...Progress in HTS Coated Conductors and Their Applications Oct 2007.pdf) They are also getting about 380 A/cm-width with 6 m runs.
Honestly, if there was a room temperature superconductor and it wasn't cost prohibitive or an environmental nightmare, they would use it regardless of how "good" of a superconductor it was.
ALTER EARTH'S ORBIT AND TILT - STOP EPIDEMICS OF CANCER, CHOLERA, AIDS, ETC.
VENUS MUST BE GIVEN A NEAR EARTH-LIKE ORBIT TO BECOME A BORN AGAIN EARTH
http://superstrun...part.gif
The formation of such zones is promoted by decreasing of temperature at the places, where the electrons are packed more closely, i.e. at the places of holes, where positivelly charged atoms are collecting the electrons from their neighourhood.
Briefly speaking, the holes are promoting a formation of isolated droplets of layered electron liquid with superfluous properties at low temperatures. The spin of these isolated droplets remains entangled (i.e. unique for most of electrons in the droplet) and as such it can be switched by using of weak external magnetic field as a whole, which enables the potential usage in spinotronic circuits.
The whole trick in HT superconductor preparation is to achieve the less or more continuous phase of highly compressed electrons throughout the whole lattice. You can think, we are trying to prepare a foamy phase of highly compressed electron fluid arranged into mesh of "pipes", which penetrates the whole crystal like neural net.
It's evident, the simple injection of large amount of randomly distributed holes isn't sufficient for such purpose, the structure matrix of HT superconductor must be specially adopted to such solution. The layered structure of YBaCuO cuprates enables to achieve this trick: you can think, it's penetrated by ordered lines of holes (formed by replacing an La3 atoms by Sr2 atoms), where the electrons are highly packed into the form of continuous superconductive "pipes", through which they can propagate in transversal waves. The strong repulsive forces between electrons must be compensated by strongly attractive forces between highly oxidized atoms in neighboring layers, so that just a tiny volume fraction of superconductive phase can be formed in such matrix. This limits the critical current density of HT superconductors.
AC is effectively as close as you can get what you are talking about. You can't carry electrons and positrons in the same space because they anihilate each other. AC works by first pushing electrons then pulling them back. The magnitude and intensity of the oscilating pulse is the AC Voltage and AC Current.
Sometimes 3 wires are used to carry current at the same frequency but out of phase i.e. (3 phase). This increases the power of the transmission.
one way to apply your concept would be to use photons. They do not interfere so you can carry as many as you like through free space. The problem is find a transport medium. Ideally a vacuum would be used. If you use fiber optics then there is significant increase in photonic resistance (i.e. permittivity descreases).
You can convert electricity into a mega death ray laser. The only problem here is that we only have photoelectric effect (PV cells) to revert the photons back to electrical energy. PVs are still very inefficient.