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

[Sunthalazar]

Sure, but you don't have to do it at room temperature, either. There are superconductors at Liquid Nitrogen temps. Certainly most MRI machines use Liquid Helium temperature superconductors. They, of course, cost millions of dollars, but they are still used quite frequently.

IIRC, LN costs about the same as milk (~$3/gallon). If the rate of evaporation wasn't too great, it would just be an on-going charge. Say it was 1 gallon/month, would only cost you about $36/year.

Obviously LN distribution isn't up to par with electricity, but in the "closer" term it certainly would be feasible for "industrial" applications. Like running the Internet backbone routers.

Re:Gift for understatement

[DrMrLordX]

Honestly, I do not think that room temperature superconductors should be necessary in order to give us incentive to utilize superconducting transistors in products of some sort. A superconducting transistor capable of functioning properly at temperatures that could be maintained by liquid nitrogen would be more than sufficient to give rise to viable commercial products, albeit only for a small niche within the greater computing market. Obviously LN2 just isn't going to work in a handheld or portable device; however, it should be simple enough to keep even a desktop processor chilled by LN2 without having to resort to frequent trips to a supplier to refill numerous dewars.

Re:Gift for understatement

[MozeeToby]

That all depends on what you consider 'room temperature'. To me, that doesn't mean actual room temperature, it means a temperature that can be achieved with small, economical cooling systems. I could see all the way down to -50 degrees C being practical for in home use. Considering the record for superconductivity is around -135 C, we're really not all that far away. In fact, seen as liquid nitrogen is relatively cheap to produce, if transistors existed above that temperature it would be possible to begin large scale experimentation now.

Also, it's important to keep in mind that we don't have a working theory for how the newer higher temperature superconductors work. It's within the realms of imagination that when we finally come up with an explaination, research will proceed much more rapidly. The highest temperature superconductors known today were found essentially by trial and error.

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]

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.

...which makes it significantly cheaper than gasoline. Here's a thought: I wonder how much energy is released as it boils, and how that compares to a gasoline combustion engine. Sure, maybe we'd need more liquid volume, but it's cheaper per unit volume... and its not a Greenhouse gas either - it's 79% of the atmosphere already!

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.

Re:Gift for understatement

[UnderCoverPenguin]

Having LIQUID NITROGEN in my desktop PC would seem to present maintenance and disaster potential an order of magnitude greater than that: what if the enclosure ruptures and explodes like a capacitor? What if it leaks nitrogen into the room and asphyxiates my cat sleeping on the floor?

Years ago, I did Unix administration for the School of Science for a small university. The server room was behind the NMR lab (with its large superconducting magnets) and I had to go through the NMR lab to get to the sever room. In fact, the sever room was also used to store a 100 litre tank of LN and 100 litre tank of LH. The tanks will not explode. In fact, they leak a tiny amount of nitrogen and helium all the time. Even in the closed sever room (it had its own AC, seperate from the building AC), this was not a problem.

Also, a PC is not like a superconducting magnet: It will not 'quench' and cause the LN to rapidly evaporate. Even if it did, a PC is not going to contain much LN - less than 1 litre. A magnet (at least back then) would have 50 (or more) litres of LN (and LH). The affect on a the nitrogen level of the 20x20 room was negligible, even at floor lever. And, if your PC did quench, the noise of the escaping gas would almost certainly wake your cat or dog (with the likely size of the relief orifice in the PC would result in a piecing ultrasonic whistle, which cats and dogs cat hear).

(FWIW, the most, be far, dangerous aspect of a magnet quench is the helium. But that clings to the ceiling. Being cold, it also condenses water vapor, forming a cloud.)

Liquid cooling?

[cjfs]

At 0.3 kelvin - just above absolute zero - these electrons flow without resistance and so create a superconductor.

So my stock fan won't quite cut it this time?

Re:Liquid cooling?

[Anonymous Coward]

Hear that "whooshing" sound? It's not a fan.

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.

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

Bad timetable.

[Tatarize]

We have no idea how far away we are. We don't fully get it and are pretty much trying substances at random. We might figure out something that works next year or never. It's not something you can predict with any accuracy.

Re:Bad timetable.

[aztektum]

So you're saying we could have something to market in 5 but possibly up to 10 years?

Neat, yes, but not really the first

[johndoe42]

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

cond-mat/0601434

Speed???

[Biff Stu]

Speed isn't only determined by on-state resistance. Capacitance & inductance matter too and will be the limiting factors for a theoretical transistor that's 0 resistance on and infinite resistance off. Such a theoretical transistor won't dissipate heat, so it won't get hot. However, heat will be dissipated somewhere else because current still must flow from high potential to low potential. Furthermore, transition times aren't arbitrarily fast, and during the transition, the transistor will dissipate resistive power; this could be a big problem for systems cooled below 4 K.

80 watts for 80K

[climate_control]

Yes, you can insulate a device, so that in almost all cases (definitely in the case of a fast-switching transistor) the main heat source is the device itself.

Here's a commercial box that cools a 2-inch wafer of high-temperature superconductor to around 80K. This box uses 80 watts including whatever other signal processing stuff is in there.

Another source (Cryogenics 42 (2002) 705-718) says that 1W of cooling power at 4K will cost you 5kW of input power using a straightforward helium compressor. This scales as 1/temperature^2 for higher temperatures, but for lower temperatures you'd switch to a different type of refrigerator.

0.3K refrigerators using helium 3 would not use more than 10kW, but this is already too much for most applications.

So the practical significance of this research is that it may be reproduced with higher temperature materials, not that we will build THz DSPs at 0.3K.

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".