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Silicon Superconductors
Diana writes "Physicists at CNRS have demonstrated superconductivity in silicon, the element long known for its semiconducting properties. High doping is the key — by substituting 9% of the silicon atoms with boron atoms, it was found that the resistance of the material drops sharply when cooled below 0.35 K. A small increase in the transition temperature is likely with further work."
Um, lots of people care. The MRI machines use super-conducting material cooled with liquid nitrogen, this might make them more efficient. Plus, when I've got my Mag-Lev skate board, you're gonna think I'm pretty cool too. Even if I
am in space.
BTW, 0.35 K = -272 C
Space is around 2.7K or, -270 C (Assuming no Extraneous Radiation)
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First of all, it's called RESEARCH! It's a very new and different bit of science--who knows where it could lead us?
Secondly, just because things are a pain in the ass doesn't mean they don't have useful applications. NMR/MRI have been dependent on low-temp superconductors (i.e. liquid He or even colder) for decades, and they're immensely important for research and medicine.
"People who do stupid things with hazardous materials often die." -- Jim Davidson on alt.folklore.urban
I work on a radiotelescope that uses receivers cooled to 4K. These use a helium refrigerator that works just like the Freon thing in your car but using helium instead of Freon as the phase-change medium. It takes three stages of cooling (with compressors and heat exchangers) to get to the 4K point. It also takes 10 kW of electrical power to cool one watt of load to 4K.
We until recently had one receiver, a bolometer, that was cooled to 0.4K using the 3He isotope of helium that has a lower boiling point. The refrigerator for this is a fist-sized gadget that uses a charcoal trap, a heater resistor and some plumbing to make a refrigerator that can be cycled to produce 0.4K for a day or so at a time. It makes many microwatts of 0.4K coldness from less than one watt of 4K coldness.
Unfortunately, the 3He leaked out and the gizmo is currently a paperweight since it was made by a very clever French guy who's no longer in the business.
You can still buy 3He refrigerators from other manufacturers, but they are two feet long. The 3He is available for several thousand dollars a bottle.
The determined Real Programmer can write Fortran programs in any language.
replacing nearly 10% of it with another element must mean that it falls into another classification.
An alloy, if you will?
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The only thing worse than an aggressively ignorant idiot is a foul-mouthed one.
In the 1830s, it was discovered that some materials acted as neither pure conductors nor pure insulators. They called them semiconductors, and they were a curiosity until the 1890s, when they were found to be useful as rectifiers and photovoltaic cells. Another 40 years later, and people started to consider them as a replacement for the triode vacuum tube, which was immensely useful but fragile and difficult to deal with.
Pure research in new directions isn't just allowed because it 'might lead to something,' it's absolutely essential in order to progress beyond refinement of the existing.
"People who do stupid things with hazardous materials often die." -- Jim Davidson on alt.folklore.urban
You forgot to put the link... http://www.twinkiesproject.com/
It means quite a bit. Strontium titanate was the first superconducting semiconductor, predicted to be so by Marvin Cohen (my theses advisor :-) and later confirmed by experiment. The general idea is that a semiconductor with multiple valleys in the conduction band into which to place dopant electrons can rapidly develop low-energy electronic states under doping, and these are the states that couple to lattice vibrations and so generate superconductivity. If you don't have a problem with the term "doped semiconductor," (which is a material that actually conducts- how do you think those electrons get through transistors on computer chips :-), then you should be ok with "superconducting semiconductor".
Curtains for windows?
Eh, just because you haven't found a material that is a superconductor at room temperature doesn't mean that there aren't any. It's easy to say "X can happen, because we have example Y", but you can't say "X can't happen, because we have example Y". All you can do is state all the places you've seen that it doesn't work. Sometimes, you can generalize those results (water from the atlantic ocean is not made of cheese, and thus we have no reason to believe that water from the pacific is either.)
Negative results are still results - they limit the problem space that you can search to find a positive result.
Pretty much anything will superconduct below 0.35K. How is this news?
Actually, no, many things do not superconduct at arbitrarily low temperature, common examples being some of the best room-temperatures conductors we know of (eg copper and gold). Pure silicon also does not superconduct, as explained in TFA, which was known for some time.
As for this being news, well it interests me because I do experimental research with superconductors. But I'm surprised it made the front page of slashdot.
make world, not war
No. You are wrong. Read up about blackbody radiation. Space is like a big cavity with blackbody radiation that's about 3k. That's the thing about electromagnetic radiation - you don't need a medium. Let me make it clear... If you brought a piece of metal into space, would it keep cooling off by radiation? No. Why? Because at 3 kelvin space would be giving it as much energy as it is shedding. The pipe and space would be at an equilibrium state when the pipe reached 3 kelvin. You see how this is real temperature? Good.
If I understand Dirac correctly, his meaning is this: there is no God, and Dirac is his Prophet. -Pauli
The doping is a small enough percentage that it still retains the crystal structure of silicon, so on a macroscopic level, it still looks and behaves like silicon. The crystal structure forces the boron to act like silicon, which is key because boron has two fewer valence electrons than silicon, resulting in stable "electron holes" in the conduction band that raise the overall mobility of electrons, and therefore raise the conductivity of the material.
So no, it's not pure elemental silicon, but it's still silicon. It's like saying that even if my tap water contains 10% impurities, it's still water.
Life would be easier if I had the source code.
Not really. No one makes a 300K->.35K cooling device. Put simply, you take a 3K->.35K refrigerator and set it inside a 300K->3K refrigerator. Since any lab or plant that is doing this sort of work already has the 300K->3K unit, using said unit is a trivial addition to the process of using the new "low temp" unit.
Wikipedia has an explanation.
The electrical resistivity of a metallic conductor decreases gradually as the temperature is lowered. However, in ordinary conductors such as copper and silver, impurities and other defects impose a lower limit. Even near absolute zero a real sample of copper shows a non-zero resistance.
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