
Closing in on high-temperature superconductivity - jonbaer
https://www.sciencedaily.com/releases/2016/09/160919132603.htm
======
pbsurf
Three groups published essentially the same results in the same issue of
_Science_ :

Greiner group:
[https://arxiv.org/pdf/1605.02704.pdf](https://arxiv.org/pdf/1605.02704.pdf)

Zwierlein group:
[https://arxiv.org/pdf/1606.04089v1.pdf](https://arxiv.org/pdf/1606.04089v1.pdf)

Bloch group:
[https://arxiv.org/pdf/1605.05661v1.pdf](https://arxiv.org/pdf/1605.05661v1.pdf)

~~~
rubidium
Thanks for sharing. I'm pretty familiar with the area, and it was fun to see
the different approaches and styles of the three groups in the papers.

Zwierlein = "we're doing solid state physics" (disclaimer: with ultracold
atoms)

Bloch: optical lattices and ultracold atoms are cool. You can do anything.

Greiner: quantum gas MICROSCOPES!

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VladimirGolovin
There's probably a serious error in the cover image caption, or the image
itself is seriously misleading. I'm quoting verbatim:

> _" This composite image contains an equation in the foreground related to
> theory research in high-temperature superconductivity, and images in the
> background resulting from high-temperature superconductivity experiments.
> Credit: Image courtesy of Penn State University"_

At least one of the images in the background is not 'resulting from high-
temperature superconductivity experiments', it's just a plain rendering of the
default preset of a Filter Forge filter 'Electricity':
[https://www.filterforge.com/filters/237.html](https://www.filterforge.com/filters/237.html)

(I am the author of this particular filter, and the founder of Filter Forge.
The 'electric' image looks a bit different on our page because we force
seamless tiling to on when rendering images for the web).

~~~
snowwrestler
It saddens me that the top comment is a technical note about the eye-catcher
image, not the substance of the article.

~~~
Dylan16807
The article doesn't have a lot of substance though. It spends a lot of time on
what the goals are and buries the few snippets of what they actually did and
measured. They have a physical simulator and a computational simulator? Maybe?
It's a mess.

~~~
drostie
Yeah, basically. From what I can tell given some work I've done in a related
field, what's happened is that they found a new way to do the math in a
theoretical model some long time ago, and it revealed some cool new
predictions within a certain temperature range, as well as some equivalent of
high-T superconductivity at some other temperature range.

Now they went to test it, which they did by supercooling potassium atoms while
using lasers to force them into one place. (Conveniently you can also use
lasers for refrigeration though I'm not sure if they did.) Then they switched
the lasers to describe a big 2D standing wave which the potassium atoms spread
out into, forming a square grid. These are called "optical lattices"; they're
difficult to work with because you don't have anything small enough to really
poke at individual atoms and even if you did you'd have to deal with how the
lasers are blasting your poker left and right... so, you just have to kind of
throw your hands up, "I am not going to care about any of these individual
atoms." However, you get some nice bulk properties: for an easy example, if
you just turn off the lasers and let stuff drift and then image it, they all
basically started from the same place and drifted according to their velocity
which is proportional to their momentum, so you can get an image of |ψ[p]|²,
the momentum-space distribution of the wavefunctions of the individual atoms.
So that's cool. But basically you have this tiny little dot of well-arranged
well-controlled particles, but you can only do bulk operations on them
(including e.g. bulk entanglements by bringing pairs of rows closer together
by messing with the lattice and cool stuff like that).

While I'm not clear what the theoretical predictions were, exactly, apparently
when they pushed the system into the first temperature regime described above
they discovered whatever their theoretical model predicted. Hooray! This has
given them some small confidence that maybe their theoretical model is a
plausible step forward for understanding high-T superconductivity.

------
Animats
By "high-temperature" superconductivity, physicists mean liquid nitrogen
temperature, not room temperature. It's progress, but cheap maglev is still a
ways off.

~~~
ptero
Liquid nitrogen is much easier and cheaper to work with than liquid helium
(probably most US high schools see freeze and break a banana or similar
experiments regularly; it costs very little).

IMO it would still be a major real world breakthrough when this is ready for
engineering use. But while this research may be a big step to that goal, it
does not yet move the problem from science to engineering.

~~~
jeffwass
I used to do a lot of cryogenics work during my PhD.

The statistic one of the professors often quoted was that "LN2 is cheaper than
milk".

Although LN2 is cheaper and more abundant, it's also 20 times warmer than LHe.
That matters a lot for applications.

To get an idea of ability to restrict thermal excitations, LN2 at 77K is
_only_ 4x 'colder' than room temperature. But LHe (4.2K) is 18x 'colder' than
LN2, or 72x 'colder' than room temperature!

~~~
bryondowd
The 4x 'colder' here really threw me. Took me a minute to realize you meant
1/4 the temperature. Strikes me as an odd phrasing, like saying "airplanes fly
23x 'lower' than LEO".

~~~
witty_username
It's odd but correct because temperature has a minimum.

We're just used to Celsius/Fahrenheit temperatures where you can't say that.

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hinkley
What is closer, high temperature superconductors, or fusion power plants?

~~~
anexprogrammer
Fusion's 20 years away. Just like it's always been since ZETA in the late 50s.

~~~
jfoutz
I always thought that was a funding thing. It seems like there are a few small
improvements every few years, because, I think people who work on that work
pretty hard.

It's that they want to build a multi billion dollar thing "to answer
questions". Since there's no immediate payoff, it follows the superconducting
supercollider path.

Also, it's nuclear power, so that's another nail in the coffin.

~~~
iSnow
I don't really think it's funding. There has - over the last 50 years - been
considerable funding from all industrialized countries. The physics of
containing a large volume of plasma and injecting cryogenic fuel and turning
the resulting energy into something usable (eg. steam) all next to each other
is simply not trivial.

Let's see how Wendelstein 7x or the announced micro-fusion devices turn out in
operation - maybe they are finally the breakthrough. I am not holding my
breath for ITER, though.

~~~
drjesusphd
Funding: [http://i.imgur.com/sjH5r.jpg](http://i.imgur.com/sjH5r.jpg)

Wendelstein 7X is impressive, but it doesn't have the facilities for actual
fusion. The best they can do is "theoretical breakeven", which has already
been achieved with tokamaks (JT-60 in Japan).

As for "micro-fusion" devices: if you're thinking of Lockheed, as far as I can
tell they're full of shit. It's an approach that was tried 50 years ago and
failed.

~~~
andrewflnr
You seem to imply that failure 50 years ago implies failure 10 years from now,
which, with all the advances in supporting technologies, is nonsensical. Do
you have any solid evidence that Lockheed is full of shit?

~~~
drjesusphd
No I don't, which is why it was a qualified statement. They've released very
little information about their design, and it's up to them to convince the
taxpaying public it's anything more than a mirror machine. How do they keep
the plasma from squirting out of the sides? That'd be the real innovation, but
they're silent on this point. Almost as if they're not worried about it.

Oh, and now it's 10 years from now? I thought they said it'd be ready in five?
Wait, three, because they said that two years ago.

~~~
andrewflnr
The other reason to keep quiet about confinement is that it's their secret
sauce. The 10 year number is a deliberately pessimistic one I pulled out of my
hat, not meant to be precise. I'm just saying, it's possible that things have
changed enough to make possible in the near future what was
impossible/impractical in the past.

------
SapphireSun
This is really important. If you can improve conduction efficiency by a
percent or two (let alone lossless) you can put solar panels on the other side
of the planet and solve global warming in a pinch by piping power to the dark
side. Right now it's about 3% at 100kV iirc which translates to ~40% losses
best case which, while almost financially feasible, would also cook the planet
in a toaster oven. :P

~~~
stretchwithme
might be a pretty long wire. Is that going to be cheaper than the solar energy
microwaved from space?

~~~
jp555
What's the difference between space-based directed energy transmission and
building-vaporizing laser space weapons?

~~~
VLM
"solar level" power density, even ten times solar level power density, is
still maybe a factor of a million too low to vaporize buildings.

Note that a 2x solar energy flux beam would still be an interesting tactical
or strategic weapon. It wouldn't melt or burn anything directly but you could
make winter streets very comfortable for protestors, or make summer streets
intolerably hot for protestors. Or you could boil off water quicker than
letting the sun do it itself, which is nice after a snow storm and not so nice
during a drought.

There are a variety of interesting optical resolution limits such that its
physically impossible to accidentally turn a "warms up a couple square miles"
mirror into a death ray of doom.

Note that like 50 years ago people were pimping 90+% effective microwave
antennas... the ground station work was done decades ago and its cheap. Now
how you get a multi-megawatt continuous microwave magnetron in orbit and
powered is the hard part.

~~~
jp555
super interesting thx! I didn't think of larger-area, lower intensity beam as
an option. Now it's got me thinking of other ideas like adding a few months of
growing season to northern & southern farms, which sounds like a cover story
of Popular Science magazine from the 70s :D

------
xt00
TLDR: The main finding is: They built a simulation and super cold 2D
experimental setup that verified that the "Hubbard" superconducting model is
validated to a high degree (for a certain temperature range), and that
electrons start forming pairs that "bunch" with empty spaces in the lattice.

~~~
dnautics
Man, I wish the title didn't suggest that high temperature superconductivity
experiments were performed.

~~~
xt00
I know, total clickbait for engineers and nerds.. A similar one would be like,
"Woz has THIS to say about new Star Wars movie..." omg, gotta click that...

~~~
labster
"You won't believe what Linus just said"

"11 programs Stallman doesn't want you to install"

------
hyperion2010
Link to the article (paywall) [0].

0\.
[http://science.sciencemag.org/content/353/6305/1257](http://science.sciencemag.org/content/353/6305/1257)

