
Hydrides come within a whisker of room temperature superconductivity - lachlan-sneff
https://www.chemistryworld.com/news/hydrides-come-within-a-whisker-of-room-temperature-superconductivity/3010030.article
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Causality1
Is there a measurement for how much power a superconductor of a given diameter
can actually conduct? Of course we're all familiar with the "resistance = 0"
concept but I don't think that means you could pump ten billion amps through a
superconductor the diameter of a hair, or does it? What other forces limit
high-density current flow besides simple resistance?

~~~
skykooler
What limits it is that superconductors can only handle a certain density of
magnetic flux; more than that will make it stop superconducting. (This
property was used in the "cryotron", an electrical switch used in some early
computers before transistors became common for the same function.) Any
current-carrying wire produces a magnetic field; so, with a strong enough
current, the magnetic flux will cause the superconductor to switch itself off.
This can be limited by using a larger superconductor, so the flux density is
lower.

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ta1234567890
What happens if a conductor (regular wire, not a superconductor), is wrapped
in a magnet that "matches" the magnetic field produced by the wire?

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simcop2387
You can do this to enhance or change the magnetic field of the magnet. Core
rope memory and such use this principle to read, write and refresh the
contents of the cores. They send a pulse down one of the lines, read line
sends one voltage, write line sends a higher one designed to flip the polarity
if necessary, and then sense the reflected pulse on the third wire, called the
sense wire.

~~~
ta1234567890
Thank you for the explanation. I'm still confused. So if a wire is wrapped in
a specially crafted magnet, then when sending an electric pulse through it the
pulse will "bounce back"?

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gok
This article is from January but things do seem to be suddenly getting
exciting around room temperature superconductors again. The preprint mentioned
in the paper became an article in Nature in May. Moreover, the fact that there
now seem to be way to design superconductive materials rather just stumble
into them could be a game changer.

~~~
lachlan-sneff
A few months back, a team reported that they'd found room-temperature
superconduction in gold/silver nanoparticles. Unfortunately, there has been no
more news about it since.

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lachlan-sneff
I wonder if the path to room-temperature superconductors involves finding ways
of containing hydrides at very high pressures, rather than finding materials
that superconduct and ambiant temperatures and pressures.

~~~
qcj
I have the feeling it will be more economical to just use a low-temperature
superconductor and cool it down with a closed-cycle cryocooler, rather than
try to get a large enough pressure vessel that can maintain such high
pressures.

~~~
velosol
A few years ago, that was the thinking when a 'high temperature' (much colder
than room temperature) superconducting cable was trialed in Germany [1].

[1]: [https://www.tdworld.com/overhead-distribution/ampacity-
proje...](https://www.tdworld.com/overhead-distribution/ampacity-project)

[2 with follow-up presentation]:
[https://snf.ieeecsc.org/abstracts/stp475-ampacity-
project-%E...](https://snf.ieeecsc.org/abstracts/stp475-ampacity-
project-%E2%80%93-update-world%E2%80%99s-first-superconducting-cable-and-
fault-current)

------
d--b
> Attaining superconductivity requires the diamond anvil cell to exerts
> pressures of up to 200GPa, two million times that of the Earth’s atmosphere.

~~~
_Microft
_At high pressure_ might be to superconductivity research what _in mice_ is to
medical research.

That doesn't mean that it is not useful to conduct these experiments. They
could give further insights into how superconductivity comes to be - or maybe
discover a superconducting material that requires high (but not too high * )
pressures to form but remains stable when they are lowered back to normal
pressure similar to how diamonds are stable at normal pressures but are
require high pressure to be formed.

* Pressures only reachable by using diamond anvils would be highly impractical to produce any useful amount of material ;)

~~~
IshKebab
I think he must meant that the headline is misleading. The holy gain is room
temperature superconductivity _at room pressure_.

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mjevans
Depending on the application, mechanically useful pressures and higher
temperatures might be good enough.

~~~
wahern
"Room temperature" already makes this concession as it means above 0C. In the
context of superconductivity I would assume "room pressure" to fairly
encompass pressures higher than 1 atm, though I don't know if there's a
practical cut-off as there is for temperature.

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Zenst
I would love a CPU that ran at room temperature.

OK, it's a cart and horse affair as it is the resistance that causes the heat,
but I'm mindful how lab work pans out into real-work. But even reducing
resisting a bit in a practical, consumer useful way has massive benefits.

~~~
cr0sh
Technically, yes, "resistance causes the heat" \- but why? Well - because in a
CPU, voltages are being manipulated.

Those voltages represent binary values. Usually a positive voltage is
designated as a binary "1" and a zero voltage as a binary "0". Putting a "1"
into a register (or whatever) is easy - just add the appropriate voltage. But
how do you change that "1" into a "0"?

You do so by "grounding" the circuit - that is, a circuit is made where the
voltage level representing the "1" is connected to the reference voltage level
that represents "0". Since that voltage level is "0 volts" (usually - but not
always - but it is usually lower than the voltage level representing "1");
that change in voltage happens to occur across a conductor, and that conductor
has some resistance, and that ultimately is what generates the heat.

ASIDE: It is possible to reverse all of this - that is, use a negative or zero
voltage to represent a "1" and a positive voltage to represent a "0", and so
on - I'm not sure, though, that this is done in common practice, but I am
certain it has been done somewhere at least once.

So - what does that mean? Well - it means that in a CPU, just by the fact that
it is manipulating voltages that represent the binary symbols "1" and "0" \-
it is going to end up generating some amount of heat. The fasting these
changes occur, the more heat that is output. The larger the voltages involved,
the more heat is output (note how this explains why, as CPUs have gotten
faster, their operating voltages have become lower).

How do you combat this? Well - it ain't easy - but what if you could, instead
of grounding a voltage representing a "1" to make it a "0" \- you instead used
it elsewhere (in some manner) to generate a "1". That is, instead of wasting
that voltage and energy as heat due to resistance, you used it instead to
perform the opposite function elsewhere in the CPU?

Well - you can - though it ain't easy from what I understand. It's called:

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

~~~
hwillis
To vastly simplify: Since one signal is zero resistance (zero loss) and one
signal is infinite resistance (zero loss), switching between the two requires
a finite time spent at a resistance between the two (nonzero loss). Every
change requires a change in entropy to represent it. This is also known as
Landauer's principle:
[https://en.wikipedia.org/wiki/Landauer%27s_principle](https://en.wikipedia.org/wiki/Landauer%27s_principle)

> How do you combat this? Well - it ain't easy - but what if you could,
> instead of grounding a voltage representing a "1" to make it a "0" \- you
> instead used it elsewhere (in some manner) to generate a "1". That is,
> instead of wasting that voltage and energy as heat due to resistance, you
> used it instead to perform the opposite function elsewhere in the CPU?

That's different and wouldn't really apply to a concept like resistance. It
also doesn't need to be the opposite function, just... something.

~~~
DoctorOetker
>>but what if you could, instead of grounding a voltage representing a "1" to
make it a "0" \- you instead used it elsewhere (in some manner) to generate a
"1"

that leans towards reversible computation, which would need a reversible
computer (getting close to unitary transformations in QM)

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m3kw9
Is it correct to think that because of entropy of heat, it is harder to make
atomic structures stable enough to form a perfect path for electrons to run
without loss at higher temps?

~~~
acchow
I hope this is the right description because it would make such intuitive
sense.

But superconductivity is also a quantum phenomenon so it probably defies
intuition.

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acd
I ponder if the sun is a really large super conductor? Since the sun has
really high pressure like in the article and it has largely a lot of hydrogen
like in the article.
[https://en.wikipedia.org/wiki/Sun](https://en.wikipedia.org/wiki/Sun)

~~~
codedokode
I don't know if it is superconductor, but plasma is somewhat conductive
because it is consists of charged particles.

