
A Superconductor That Works at -70 °C - jonbaer
http://www.technologyreview.com/view/542856/the-superconductor-that-works-at-earth-temperature/
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MCRed
This is pretty huge. The last major break thru was getting superconductivity
in Y1B2C3O at liquid nitrogen temperatures (-200 C) back in the 1980s. I
worked in a lab with the discoverer of this phenomena, Dr. Paul Chu.

While -70 is still damn cold, it should be achievable a lot more cheaply than
having to cool things with LN2, so hopefully-- cross our fingers-- this will
lead to the breakout of superconductivity into broad industrial use (and maybe
the mainstream consumer market) that people have sought for decades.

BTW- while in that lab I used a variation of the meissner effect to design a
memory circuit that was theoretically buildable at the time- static RAM that
was superconducting. (and basically, the essentials of a transistor were there
so logic gates could be built from super conductors, that was the thought
experiment I was doing.)

Since heat is a major concern in CPUs, the ability to be superconducting (and
thus producing no heat) would be a huge boon for computation. Of course
initially this wold be at scales much larger than current lithography and thus
only for specialized applications. But who knows.

With effort the cost of keeping a CPU at -70 should come down dramatically the
way battery capacity per dollar has... or dare we hope the way flash density
has.

~~~
AnimalMuppet
> Since heat is a major concern in CPUs, the ability to be superconducting
> (and thus producing no heat) would be a huge boon for computation.

But (if the superconducting transistors worked like current CMOS, which is a
big if): While there would be no power draw or heat dissipation at steady-
state, there would still be some when gates switched, correct? And if so, you
could still wind up with pretty significant heat dissipation...

~~~
ant6n
I thought most of the heat nowadays is created by leakage. The rest by the
semiconductor. Not sure how a superconductor would help here.

~~~
XorNot
SQUID devices can be made switchable by the presence of an applied magnetic
field, if I recall correctly. So you could build your superconducting computer
entirely out of superconducting components.

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Animats
For low values of "earth temperature". Apparently, when hydrogen sulfide gas
is compressed to very high pressures and cooled to -70C, it becomes a
superconductor. That's an interesting physical phenomenon, but lots of
materials have unusual physical properties under extreme pressures. Chemicals
can be forced into a crystal lattice even when they don't stably bond that
way.

Still, it's a new data point. Maybe someone will find something that's both
stable under standard conditions and superconductiong.

~~~
svckr
Plus, at that temperature, you can easily keep the conductor cooled with
frozen CO2, which is pretty easy to produce / readily available.

~~~
krasin
Thermoelectric cooling ([1]) can reach such temperatures, which will not
require any gas consumables. However, it could be more energy-efficient to
cool with CO2. I have not done math for that.

1\.
[https://en.wikipedia.org/wiki/Thermoelectric_cooling](https://en.wikipedia.org/wiki/Thermoelectric_cooling)

~~~
rcthompson
Most biology labs have a -70C or -80C freezer (or several) in their lab. As
far as I know, they work the same way as the freezer in your kitchen. Since
they're so widespread, I'm assuming this is probably the most economical way
to achieve temperatures of -70C. But that might change depending on what
volume needs to be cooled to that temperature.

~~~
StillBored
Funky refrigerants...

The following has an evaporator temp of -96C to -73C, and a condensing temp of
-29C.

[https://www.chemours.com/Refrigerants/en_US/assets/downloads...](https://www.chemours.com/Refrigerants/en_US/assets/downloads/h53011_Freon23_for_vlt.pdf)

If you scroll down in the PDF you can see a comparison with R-503 and R-13,
two other low temp refrigerants.

But you can't just put that in a normal refrigerator.

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Rexxar
For information, this "news" is two months old. One of the multiple articles
on this: [https://www.newscientist.com/article/dn28058-warmest-ever-
su...](https://www.newscientist.com/article/dn28058-warmest-ever-
superconductor-works-at-antarctic-temperatures/)

------
KMag
Note that hydrogen sulfide is in the realm of hydrogen cyanide in terms of
toxicity. (Unfortunately, Wikipedia doesn't have comparable LC50 times for
humans, but for H2S we're talking 600 ppm for 30 min and HCN is 357 ppm for 60
min.)

We're unlikely to see high-pressure H2S lines running through residential
neighborhoods any time soon.

~~~
knodi123
Hydrogen sulfide is in farts. About one percent, if I recall correctly?
"Silent but deadly" indeed.

~~~
dexwiz
If you were sitting in a room of 100% pure fart, pretty sure you would die.

~~~
leoc
Signs are on it: [http://www.bbc.com/news/uk-northern-
ireland-27754408](http://www.bbc.com/news/uk-northern-ireland-27754408) .

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paulmd
To my untrained eye, the Meissner effect appears to be the most obvious
connection between the previous high-temperature superconductors and this
finding.

If intense pressure causes superconduction, then perhaps the Meissner effect
is a manifestation of the same phenomenon. If the Meissner effect expels
magnetic fields from the material, then perhaps this effect also causes the
material itself to be compressed physically in response, or something like
that.

Disclaimer: I know nothing about superconducting physics, but I did stay at a
Holiday Inn Express last night.

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skimpycompiler
How come physics can't predict the warmest superconductor?

~~~
analog31
Disclaimer: I'm a physicist but have no expertise in solid state physics. I
remember when the whole high-Tc thing started. My recollection is that the
discovery broke what was at the time considered to be the mainstream
understanding of superconductivity. And, a more comprehensive and satisfactory
theory has not yet emerged. As a result, we're in a sort of tortoise-and-hare
race between theory and experiment, where each one advances a bit when the
other one catches up and makes a new discovery.

~~~
weland
Disclaimer: I'm (technically) an engineer, not a physicist, but I took a
course on this back in uni, and as far as I can remember, you're correct. The
gist of it is that BCS theory, which satisfactorily explains conventional
superconductivity, fails to predict the behaviour of high-temperature
superconductors, and there simply isn't a better model available at the
moment.

For any sane individuals reading this, the answer is "We're trying really hard
but so far we haven't been able to deduce a formula for the highest
temperature."

I'm not very optimistic with regards to this ever happening. I remember
reading a paper regarding one of the many high-temperature superconductors,
BSCCO; it has a crazy crystaline structure, it's quite unlikely that we'll
ever come up with an analytical model describing its superconductive
behaviour.

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thecopy
If we could run a CPU with no heat generated, what limits the clock-speed? The
speed of the electric potential-change in the conductors?

~~~
SEMW
> If we could run a CPU with no heat generated

Nitpick: not much heat generated, but not _no_ heat. There are fundamental
lower bounds on the entropy increase caused by doing irreversible computations
(Landauer's principle), superconductors or no superconductors. TAANSTAAFL: the
universe won't let you compute for free.

As for what limits the clock speed: for one thing the speed of light -
information still has to get from one part of a CPU to another.

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aidenn0
-70C is above the dry-ice sublimation point, though just barely, so perhaps not enough to be useful; another 10C and it really could be.

~~~
DasIch
There is no dry-ice necessary. You can cool something down to -70C and lower
with a freezer as used in biology or medical labs. Such a freezer isn't even
that fancy, they look and afaik work pretty much like the household appliance
variant.

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imaginenore
What do you guys think of these room temperature (and above) superconductors?

[http://www.superconductors.org/400K_SC.htm](http://www.superconductors.org/400K_SC.htm)

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imaginenore
This was actually known for at least a year:

[http://www.superconductors.org/sulfhydr.htm](http://www.superconductors.org/sulfhydr.htm)

