
Twisted graphene has become the big thing in physics - furcyd
https://www.quantamagazine.org/how-twisted-graphene-became-the-big-thing-in-physics-20190430/
======
intenex
Fairly shocking to me that Yuan Cao received literally a single glancing
mention here, but he was clearly the one who actually made the pivotal
discovery, and is the first author on the Nature paper
([https://www.nature.com/articles/nature26154](https://www.nature.com/articles/nature26154)),
and was the one named to the Nature 10 in 2018 for his discovery.

Really mind boggling that this entire piece focuses all the attention on his
supervisor and almost neglects to mention him at all.

~~~
deugtniet
Usually the grad student does most of the work, but the ideas and direction
comes from the supervisor. It's normal that the supervisor funds, directs and
communicates the work that's being done. More often than not, the supervisor
has a better idea of the big picture and the implications of the work than the
grad student, so it's natural that the supervisor talks to the press.

For example, I'm a grad student, in a department where my supervisor would
talk to the press on work that I would have done.

~~~
threetwoone321
In CS related fields, in particular ML and CV, this is absolutely not the
usual situation except perhaps in the beginning of the PhD. Perhaps it's more
common in fields where the research is done on top of a heavy investment in
infrastructure/equipment that is lead by the professor, e.g. in physics and
biology?

~~~
astazangasta
In my experience in biology new professors provide a lot of ideas, old
professors just steal new ideas from their students and post docs.

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sagitariusrex
>Even without superconductivity, ordinary computers and other electronics
could get a huge boost in performance versus cost from twistronics, due to the
fact that entire complex electronic circuits could in theory be built into a
few sheets of pure carbon, without needing a dozen or more complexly etched
layers of challenging materials common to today’s chips.

------
ezequiel-garzon
Does anybody know if the environmental impact of graphene is supposed to be
any better than that of plastic? Does it break down more easily as it is so
thin? I’m worried we may outdo ourselves with the magic compound of the
century...

~~~
ekingr
Another major 'environmental' impact that may be very nefarious is the health
effect of such nano-materials.

We don't want to re-create all the mess that we have today form asbestos --
which was also a wonder-material at the time.

~~~
village-idiot
The problem with asbestos wasn’t really the toxicity per se, it’s that the
companies using it hid the toxicity to avoid having to do all the expensive
safety steps that would let them use asbestos without killing people. We can
avoid this with carbon nanotubes and similar if we’re honest about the risks
and careful with how we handle them.

~~~
hanniabu
This will probably happen again given all the money that's on the line.

~~~
village-idiot
The fact that we’re talking about it here implies that we’re in a better place
than we were a century ago.

~~~
dasil003
A century ago yes, fifty years ago I'm not so sure, thirty years ago almost
certainly not.

------
gigatexal
Yes. There’s not applicable commercially viable things based on graphene yet.
But superconductivity will be a revolution in many ways and especially in
computing.

~~~
mailslot
Superconductivity would revolutionize transportation, low cost medical imaging
with MRIs, and weapons. Lots of weapons.

~~~
scotradamus
You're forgetting the two most important; energy storage and transport.

~~~
m12k
Yeah, imagine if we could more or less losslessly transfer electricity over
vast distances. Massive renewable energy farms could be built wherever there
was sun/wind/rivers whether the energy consumers are close or not. Energy
could be sent to pump water into reservoirs as huge centralized batteries. The
problem with 'what happens when the sun isn't shining/the wind isn't blowing'
could be sidestepped because it's always sunny/windy somewhere, so we just get
the power from as far away as needed.

~~~
fsh
People seem to underestimate how efficient regular power lines are. The
continent-spanning european power grid has a total transmission loss of about
6% using 19th century technology (transformers and copper wires). Modern high
voltage DC lines can perform even better. The main limitation seems to be that
people don't want to have power lines in their back yard. Not something that
superconductors are going to sove.

~~~
kingkongjaffa
Also the cost of a equivalent superconductor network would be an order of
magnitude more expensive that what is essentially room temperature metal
cables with very basic technology - transformers, insulation, and switchgear.

~~~
londons_explore
A superconducting power network could be built today - it would consist of a
pair of ceramic superconductors suspended in a liquid helium pipe, wrapped
with 3 feet of insulation.

Every few kilometers, one would need liquid helium pumping and chilling
plants.

Total helium losses to leakage wouldn't be too big. Electricity transmission
efficiency would be reduced by all the chilling gear running, but still better
than regular conductors.

The only real barrier is cost. Not even the cost of the superconducting
material. You can't hang a 6 feet diameter pipe on pylons across the nation -
you're going to have to bury it, and that's going to get exxxxxpensive fast!

~~~
stupidcar
> The only real barrier is cost.

I feel like this could almost be a slogan for the human race at this point.
Our grasp of science and engineering has reached a level where's there's very
few things we might want to build where we couldn't conceivably do it. We
could build the most outlandish megastructures, infrastructure and space bases
if we really had to, but it all just costs too much.

~~~
londons_explore
"It's expensive and we couldn't find investors" really means "It's a lot of
work, and nobody thinks it'll be worth it".

We might be able to anything, but the capitalist system stops us doing things
that don't look profitable.

~~~
naasking
Profitability at time X is a pretty decent heuristic for whether something is
worth doing at time X.

~~~
danharaj
How do you know that? Unknown unknowns.

~~~
naasking
Unknown unknowns are more likely to cause problems and delay completion, not
accelerate development.

------
alanz1223
Holy guac, room temperature superconductivity seems almost science fiction-y
but just imagine the disruption it would make. I would be particularly excited
to experience how much electric motors and energy transfer/storage and
conversion would improve.

~~~
fsh
Apparently they reached superconductivity at 3K. Hardly room temperature.

~~~
zamalek
The thing is they can use it to understand superconductivity because there are
vastly fewer variables involved. It could _lead_ to room-temperature
superconductivity, assuming it even exists.

------
keyle
Pardon my interruption but I searched for 'use' or 'usage' and came up empty.
Anyone can tell a regular guy why it's a big deal and what are the
applications? ta

~~~
EugeneOZ
Superconductors = flying cars. Finally they are working on something useful!

~~~
Haga
Better make watertight social control devices if you want to hand everyone
alien nose hair trimmers that can level city's. Same for the flying cruise..
Cars.

Some exponential tech, always seems to be 30 years away from legacy humanity.
Thank you moderators.

------
golergka
> Pablo Jarillo-Herrero is channeling some of his copious energy into a
> morning run, dodging startled pedestrians as he zips along, gradually
> disappearing into the distance.

Can someone please write up TL;DR about the actual science without the details
on what kind of coffee did the author sip while taking the interview?

~~~
logfromblammo
When two sheets of graphene are stacked, and twisted with respect to one
another, they form a metameterial, with properties partially dependent on the
twist angle.

At a twist angle of 1.1 degrees, the energy required for an electron in one
sheet to tunnel to the other sheet drops to zero.

The problem is that certain angles represent a lower-energy state than others,
so twisting to a magic angle also requires overcoming some buckling and
creasing in the individual sheets, that allow regions to locally align to a
non-magic angle (like zero degrees). This confounds measurements of the
properties of the metamaterial.

Certain angles have been shown to exhibit superconductivity. While less useful
than previously discovered superconductors for the purpose of moving
electrons, these are more useful for studying superconductivity itself,
because the superconductor is 2.5d, composed of a single type of atom, each
with identical bond configurations. A lot of the variables that appear in
other superconductors drop out.

~~~
golergka
You're a much better popular science writer than the author of the original
article. Thank you.

------
sgt101
No mention of ballistic conductivity in CNTs which is well known, this is
obviously very different?

------
plutonorm
Where'd all the intelligent comments go? Hackernews used to be a cut above
when it came to an intelligent comments section. Where'd all those people go,
is there a new place to hang out?

~~~
homarp
If you know th new place, you know the first rule of the new place...

A nice intro to superconductors
[http://www.superconductors.org/uses.htm](http://www.superconductors.org/uses.htm)

the history of graphene, the "next best thing" since forever:
[https://graphene-flagship.eu/material/Pages/The-history-
of-g...](https://graphene-flagship.eu/material/Pages/The-history-of-
graphene.aspx) (previous HN discussion -
[https://news.ycombinator.com/item?id=8751946](https://news.ycombinator.com/item?id=8751946)
)

------
rezeroed
Is this a bigger thing than borophene which was a big thing a few weeks ago?

~~~
phkahler
I'm gonna say "no". This is only relevant in that it might lead to better
understanding of superconductivity. When the models can predict this, they
will have made progress.

------
rubyn00bie
So... I’m an idiot but I have a question: could this theoretically allow for a
battery that never loses a charge and/or charges instantly?

FWIW— I literally know almost nothing about superconductors...

~~~
soulofmischief
No, because that would violate the Law of Conservation of Energy, which
according to our current understanding would imply that this form of
"perpetual motion" is impossible as long as the system experiences some sort
of load. [0]

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

~~~
rubyn00bie
I don’t think I’m talking about perpetual motion at all...

When I say never loses a charge I don’t mean it’s limitless capacity. I mean
it could be charged 1,000,000 times without any affect on the capacity of the
system? Maybe a better way to say it, a battery that does not degrade with
each use.

Superconductors allow for the perfect transfer of electrons without any loss?
So like if I had a giant earth sized graphene wire superconductor for this
example: could I have the energy travel around the ring indefinitely so long
as it’s closed?

~~~
soulofmischief
Ok I see, by "not losing its charge" you meant not wearing down from repeated
use. Technically speaking the charge would be the amount of electrical
potential energy stored in the device.

This system is still subject to the laws of thermodynamics, however.

AFAIK _ideal_ superconductivity does not exist outside of theoretical physics,
just as ideal platonic solids do not exist in the real world. Things get bumpy
close up, and then they get fuzzy.

Even if you could maintain a "perfect loop" of electrons along a wire,
perfectly insulated from outside forces including EMI and gravity, any
observation of the system would still introduce entropy from the outside world
and eventually degrade the system unless it is self-correcting.

An ambient self-correcting conductor would be a _massive_ breakthrough.

~~~
gingabriska
Charge is not amount of electric potential.

Charge is a property of matter which causes experiencing a force when placed
in an electric field.

Strength of the electric field is electric potential.

And charges arrange in some form under this field which wouldn't be so in
absense of this field and how tight is that form depends on the strength of
electric field. And this can be used to perform some work but this is not
storing charge as the total charge before arrangement is same as total charge
after arrangement there is no new charge added. We are storing electric field
here.

In all such storage devices, strength of the field goes down after sometimes.

No I don't know how it can help in case of batteries but assuming you use
capacitor to store electric field the leakage can be decreased by using better
insulation which in many cases is thicker and the capacitor is limited to some
specific size, if you can decrease the surface area of the conductive plates,
you are able to use thicker insulation which results in lower leakage so
graphene can help here as it's just one atom thick.

~~~
soulofmischief
> Charge is a property of matter which causes experiencing a force when placed
> in an electric field.

From Wikipedia [0]:

"A battery's capacity is the amount of _electric charge_ it can deliver at the
rated voltage."

Another way of saying this is that a battery can store potential electric
charge which is _discharged_ from the battery during use. The maximum
potential electric charge a battery can store is its capacity.

Similarly, a rock raised above your head is not "storing gravity", but it
still contains gravitational potential energy.

When we talk about batteries however, we tend to colloquially refer to this
electrical potential as "charge" due to the way words like "charger" and
"discharge" have entered the vernacular. Phrases like, "How much charge does
your phone have left?" has become increasingly common.

This is distinct from the definition of electric charge that you lifted from
Wikipedia's page on "electrical charge". It's just the way language has
evolved.

> And charges arrange in some form under this field which wouldn't be so in
> absense of this field and how tight is that form depends on the strength of
> electric field. And this can be used to perform some work but this is not
> storing charge as the total charge before arrangement is same as total
> charge after arrangement there is no new charge added.

We are not measuring the total charge. We are measuring the electrical
potential across a circuit. The total "charge" remains the same, but the
electrical potential decreases when the battery discharges.

[0]
[https://en.wikipedia.org/wiki/Electric_battery#Capacity_and_...](https://en.wikipedia.org/wiki/Electric_battery#Capacity_and_discharge)

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Roark66
It is a really cool discovery, but it is still not room temperature
superconductivity...

------
tengbretson
It's great that now that regular graphene has become ubiquitous and has
delivered on all of its promises to revolutionize tech we have something new
to look forward to.

~~~
ianai
Is there a list of devices regular graphene has made possible?

~~~
rishav_sharan
I believe he is being sarcastic

~~~
dundercoder
Rats. I got excited for a second.

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harryking
Its quite shocking to see that the hard bonded carbon sheets can also move in
spite of their large forces of attraction betweeb them . Well its other
effects would be overwhelming ..

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PunksATawnyFill
YAAWWWWN.

Graphene was going to transform everything. Years ago.

------
mystikal83
Vittoria, a tire company have used Graphene tech of sorts in their bicycle
tires: [https://www.vittoria.com/us/graphene-
technology](https://www.vittoria.com/us/graphene-technology)

