
High Temperature Superconductivity Record Smashed by Sulphur Hydride - jonbaer
https://medium.com/the-physics-arxiv-blog/high-temperature-superconductivity-record-smashed-by-sulphur-hydride-c853795079bb
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throwaway_yy2Di
Tangentially, the metallic hydrogen mentioned is one of the craziest chemical
substances to possibly-exist [0].

Besides likely being a room-temperature superconductor (at ridiculous
pressures, like 500 GPa), it's postulated to be metastable -- like diamond,
you could create it at pressure, and it might stay a solid metal at STP
conditions. It's postulated to be made of atomic hydrogen -- lone H atoms,
without the molecular bonds of H_2. The recombination energy H + H -> H_2
suggests [1] it's the most energy-dense chemical fuel that exists, with 20
times the specific energy of {H2 + O2}. It could allow [1] rocket engines with
I_sp of 1,700 seconds -- four times higher than LH2/LOX. It's thought to be
the main phase of hydrogen inside the planet Jupiter [2] and responsible for
its dynamo [3] (but as an ordinary conductor, not a superconductor). It's also
speculatively a structural material, one that's less dense than water [4].

It _might_ have been created in a lab, in 2011 [4], but it's not clear.

[0]
[https://en.wikipedia.org/wiki/Metallic_hydrogen](https://en.wikipedia.org/wiki/Metallic_hydrogen)

[1]
[http://www.nasa.gov/pdf/637123main_Silvera_Presentation.pdf](http://www.nasa.gov/pdf/637123main_Silvera_Presentation.pdf)

[2]
[https://en.wikipedia.org/wiki/Jupiter#Internal_structure](https://en.wikipedia.org/wiki/Jupiter#Internal_structure)

[3]
[https://en.wikipedia.org/wiki/Magnetosphere_of_Jupiter](https://en.wikipedia.org/wiki/Magnetosphere_of_Jupiter)

[4] [http://www.nature.com/news/metallic-hydrogen-hard-
pressed-1....](http://www.nature.com/news/metallic-hydrogen-hard-
pressed-1.10817)

~~~
Xcelerate
The metastability at STP is particularly intriguing. I wonder what quantum
chemistry calculations have been performed on this material. I need to look
this up, and maybe perform a few of my own!

Supposing that we can actually generate enough pressure to generate metallic
hydrogen at some point, I wonder what the downsides of the material would be.

~~~
542458
> the downsides of the material would be

Well, considering how energy-dense it is... As a construction material,
wouldn't it be more than a tad dangerous if it ever caught on fire?

~~~
andrewflnr
It wouldn't so much catch on fire as revert to gas, straight from solid to H2.
Otherwise known as an explosion. _Then_ maybe you get burning hydrogen.

~~~
ars
Oh, there will be fire. The amount of energy going from H to H2 is more than
there is from H2 to H2O.

If this really is atomic hydrogen it holds a ferocious amount of energy.

[https://en.wikipedia.org/wiki/Atomic_hydrogen_welding](https://en.wikipedia.org/wiki/Atomic_hydrogen_welding)

~~~
andrewflnr
Yes, my point was that it doesn't make any sense to call that a fire. H(s) to
H2(g) is a highly exothermic phase change. Fire is oxidation.

~~~
ars
That's not a phase change (despite the solid to gas), that's a chemical
reaction.

Fire is oxidation yes, but despite the name oxidation does not require oxygen,
it just requires electron transfer, which happens here.

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bainsfather
This article is science writing done right.

All the information is there, but written clearly, without much jargon. A
layman could understand it well enough, a physicist can understand it as well
(the 'detailed' information hasn't been deleted or mangled by a journalist not
understanding what they're writing, just presented clearly). And the graphs
they show actually tell you what you want to know. Fantastic.

~~~
TheOtherHobbes
Yes, it's very, very good - a joy to read.

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ableal
_" [...] have measured sulphur hydride superconducting at a temperature of 190
Kelvin (-83 degrees Celsius). There is a caveat, of course. The material has
to be squeezed at pressures greater than 150 gigapascals — that’s about half
the pressure at the centre of the Earth."_

And 1.5 million times the atmospheric pressure at sea level ...

~~~
colechristensen
Put in a different, less unreachable comparison, the yield strength of kevlar
is 3.6 GPa (tension) and diamond forms between 4.5 and 6 GPa, w (compression)

It's been 60 years since we first synthesized diamonds, and back then they
were capable of generating 10 GPa, that's only a factor of 15.

~~~
akiselev
Another comparison: the highest pressure we can create without shock waves is
300-400 GPa with a diamond anvil cell [1]. With shock waves we can create
momentary bursts of up to 100 TPa

[1]
[http://en.wikipedia.org/wiki/Diamond_anvil_cell](http://en.wikipedia.org/wiki/Diamond_anvil_cell)

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perlgeek
When I studied physics five years ago, my impression was that nobody really
understood high-temperature superconductivity.

There were some mathematical models, and some professors who claimed to
understand it, but nobody was able to give a coherent explanation to the
(mostly nearly finished) students, much less predict which materials would
exhibit hight-temp superconductivity.

Does anybody know if that changed significantly? The article reads as though
the measurements were inspired by the theory, which is always a good sign.

~~~
bradleyjg
Although this is a high-temperature superconductor in the literal sense, it
isn't the kind of high-temperature superconductor that no one understands.
Those are the cuprates (and now iron based exotica).

What's really interesting about this potential discovery isn't just that it
exhibits superconductivity at a relatively high temperature but that it seems
to be a conventional superconductor. That should give some insight that a
slightly better cuprate might not.

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jlarocco
Completely off topic, but I really hate articles where all I initially see is
a headline and a large, unrelated image.

I hope the trend dies quickly...

