First Superconducting Transistor Created

holy_calamity writes "New Scientist reports that the first working superconducting transistor has been created, by researchers at the University of Geneva. Field effect transistors with zero electrical resistance would allow much faster operations. Only drawback is they need to be supercooled, something that may be addressed by improving the materials used."

Comments

Gift for understatement

[Raul654]

"Only drawback is they need to be supercooled, something that may be addressed by improving the materials used." - that last part is a bit of an understatement. We're still decades (centuries?) away from room temperature superconductors.

Re:Gift for understatement

[gumbi west]

Supercooled means liquid helium or less. This is not the same (and about 2-5 times more costly) than liquid nitrogen cooled. There are superconductors that work at liquid nitrogen temperatures, but that cannot be pulled into wires that can carry the same current as the supercooled superconductor materials (or that was the state of the art when I last checked around 2000) so they are not used for very large magnets.

Re:Gift for understatement

[3waygeek]

Back in the 80s, I remember LN pricing (in commercial/industrial quantities) being around $0.05 per liter (roughly $0.20 per US gallon). This FAQ suggests that the price is now around $0.50 per gallon in quantity.

Re:Gift for understatement

[Anonymous Coward]

so they are not used for very large magnets.

The wire drawing issue doesn't exactly help, but the main reason is Type I vs. Type II superconductors - the low-temperature metallic superconductors have a kind of superconductivity (Type I) that doesn't break down even in quite strong magnetic fields. However, the liquid-nitrogen (relatively-)high-temperature ceramic superconductors lose superconductivity (Type II) beyond a certain field strength. Which is very bad if you're using them for magnetic resonance imaging or particle acceleration (note how the LHC failure involved liquid helium cooling) which depend on generating and switching really strong magnetic fields generated by superconducting supermagnets, but doesn't matter so much if you're using them for computing or power transmission (with due care and attention to the strength of magnetic fields to avoid sudden catastrophic breakdown...).

Re:Gift for understatement

[hotdiggitydawg]

Just answered my own question...

Re:Gift for understatement

[Baron Eekman]

You're half right.

Two facts:
1) all superconductors superconduct better at lower temperatures
2) all superconductors superconduct better at lower magnetic fields

Basically, you can think of it as both temperature and magnetic field introducing a kind of disorder (causing Cooper pairs to break up, destroying superconductivity).

Type I superconductors don't allow any magnetic fields, Type II allow up to certain field strengths, depending on the material and also on temperature. (This is a 'competition' between the two important length scales in a superconductor: the coherence length--size of a Cooper pair; and the penetration depth--up to which distance a magnetic field still penetrates into the material).

In fact, the most important drawback of the high-temperature superconductors (up to about 140K), is that at those higher temperatures they don't allow for high magnetic field nor high current. Also, they're hard to produce on a large scale. Still it's commercially viable these days to use superconductors for current transport at liquid nitrogen temperatures.

Not really news

[Anonymous Coward]

Josephson Junction has been used for switching in superconductors since I was a kid.

http://en.wikipedia.org/wiki/Josephson_effect

Neat, yes, but not really the first

[johndoe42]

As far as I know, the first superconducting transistor was reported in 2006:

cond-mat/0601434

Re:Liquid cooling?

[p0tat03]

Yes they do.

Re:Liquid cooling?

[nbates]

I think the parent's point is that if you put a fan in an isolated box, the average temperature inside the box will increase.

Of course that if you have cold air somewhere you can move it using a fan to decrease temperature in another place. Or you can remove warm air as long as you have a source of colder air available.

And of course that moving air can aid you at lowering your body temperature by assisting you in transpiration.

The parent is just being pedantic.

Superconductors cannot be supercooled

[Tweenk]

Use of the term "supercooled" in this context is bogus. Something is supercooled if it remains a liquid, even though it should be a solid at those conditions (or it remains a gas where it should be a liquid). If you put a glass of very clean distilled water in a freezer you'll find out that you can cool it down to -7*C or lower without freezing. It will momentarily freeze if you drop a snow flake into it though, or when you hit the glass with a screwdriver.

(For the curious: this is because extremely small crystals and droplets have higher free enthalpy than the bulk phase due to surface effects, so their formation is inhibited.)

This has nothing to do with superconductors, because they are always solids and cannot be supercooled. For superconductors you're looking for "cooled below its critical temperature", but I admit that it doesn't sound as good as "supercooled".